Well, will that be very difficult? . I want to create posters of music groups for my sims, and I want to think that it is not very difficult... some tutorial, if it is very difficult, I will have to give up. But maybe it's not and I can create frames of my favorite photos and put them in the game... thanks

Several ways you could do this.

One would be to make a recolour of one of the Maxis paintings. So choose the painting you like and create a recolour.
Tutorial here: https://modthesims.info/showthread.php?t=102356
Templates of the Maxis paintings here: https://modthesims.info/showthread.php?t=43450

A more difficult way would be to create a new object mesh (photo frame), tutorials for that would depend upon which programs you want to use and your skill level.

Easiest way is to have your sim paint the picture you want in-game on the easel, your sim needs to have a good creativity skill for this. You can click on the finished art to frame it.
https://www.youtube.com/watch?v=56z35X-6YLQ

The easiest would be to make recolors of already existing wallhangings, either ingame ones or CC ones.

Poppet has a somewhat simpler recoloring tutorial here (works for items that don't have special textures or materials) - https://poppet-sims.tumblr.com/post/54039893647
You also need a picture editing program (Gimp, Photoshop, or similar) to edit the texture.

The original DDS utilities link wasn't working a few days ago, but there's a download here.

Personally, I don't use the Photo Studio and templates (I don't know if those templates mean you don't need to go the way around a picture editing program?). I just mark out the area and copy/paste the picture I've got over the old one, using a picture editing program. That works fine, too. If you've got a difficult item to work with, it's possible to extract the UVmap (the area on the texture the various pieces of the mesh uses) and get the exact lines you need to work inside, but most of the time you can make do without.

hey!, I'll try it, but I thought it was simpler, use my personalized poster that an author of this page made, and change the image with another one, but no, it's not that easy, I'll try it, but I don't think I'll succeed, thanks for the tutorials!!

It would be good if someone made a tutorial to change a poster, maybe I would understand something, so I have no idea :/

If you use the method in Poppet's tutorial, changing the texture of a poster is the same as changing the texture of a chair, a table, a deco object, and most other items.

For a poster or painting, you often just want to change the picture, so you find the image you want to use, and in the image editing program resize this to fit inside the boundary of the poster image in the texture, and save as a new image. Then continue the tutorial. There's really no need for a different tutorial just because you're recoloring a different thing.

There are exceptions - things like lamps and lights (the other tutorial above shows how to recolor multi-state items), anything that doesn't have a texture and/or needs changes via the TXMT, items where you need to select a particular object (bedding), items that need extra CEPs, and probably a few others too. Most of the time you'll know something is wrong if you don't get the expected result or end up with an empty package in SimPE, or the recolor doesn't show up ingame.

If you have the patience to sit through a 40+ minute tutorial (or don't mind skipping ahead to the parts you need), here's one from Youtube that shows the editing process, too:
https://www.youtube.com/watch?v=QgJWLSBRVKQ
(Editing is similar in any image editing program, you can use whichever you want, but the tools are likely going to be a bit different from program to program)

This one shows photostudio, but without any editing in a picture editing program:
https://www.youtube.com/watch?v=fPj_By3DmfE

I will see that tutorial, thanks for your help, a curious thing happened to me, once I use a family from the drawer (one created by Maxis), they have a child (twins!), one naturally and one of them is from another skin color… it's strange!! With my Chrome browser I can't open another thread, but if you read this... Do you know why that happened? (it's not racism, it's just curiosity, one twin has the parents' skin and the other is different!!)... I don't have genetic mods, or anything like that.

There's an explanation of how genetics (inluding skintones) work, here: https://sims.fandom.com/wiki/Genetics#Skintones

My guess is that either the family had some hidden recessive skin genetics that showed once they had their kids, or you had a skin in your game you didn't know was geneticized, that fell within the range of the skins of the parents. It's possible to find out with for instance SimPE, by checking the values.

Normally if you just pick genetics in CAS, the sim gets two genes for that particular thing (skin/hair/etc.). In some cases, if you've played with genetics using the pacifier in CAS, bin-sims can already have recessive genes in their genetics than what shows on the sim. Some of the maxis-sims in the bin seem to not be directly from CAS, as a few of them have known bugs (like the Ottomas' twin pregnancy having issues), so it's likely they also have recessive genetics.

I just wanted to drop this extra info:
I followed Poppet's tutorial yesterday in order to recolour wall art (The one with the 3 images of parrots), essentially like a poster.
All that changed was really just what object to choose in object workshop. You can follow the tutorial pretty easily but substitute the chair that the tutorial uses as an example with a poster you wish to recolour.
I hand-painted my recolour but you can change the picture of it and do anything you want in the image editing program.

Thank you very much, for that article, I have read it and it is not what happened, this family in Spanish is the Rodríguez (no idea what their last name is in English, The parents have no relatives, they are unique, that is, Maxis created them and left them in the drawer, maybe that's why? They give them random genetics?), the father had an alien son (he was looking at the stars and...), Then with his wife he had two twin girls!, traditional method of wohoo (or in Spanish ñiqui-ñiqui), and the two twins are different in hair and skin, one is much darker, I think rank 7 (0 would be very white, 8 would be very black), the family I put them at rank 3 or the normal range of maxis, since they are sims created by maxis, not by me... I'm going to download that arrangement, it never hurts to have all the arrangements of the maxis's carelessness. Later I will play and take a family photo and you tell me.

By default, there's only 4 regular skintones in TS2 (called S1 to S4, plus alien, and some special skins/overlays), so if they're showing up with darker or lighter colors (or entirely different skins) than within the range of the parents, it's possible you have some geneticed skins in your game.

Yes, I have some special skins, but it seems strange to me that both parents have children with totally different genetics, here I put a photo, I made them have another child and other twins were born, this time boys and it happened the same as with the girls, They are different, one light and one dark (it would be tone 2 and tone 4, according to Maxis). So... they assign random genetics to the sims that they have created and put in the drawer, right? Later I'll enter the game and take a photo of the new twins...hahahahaha
P.S: I have a default special skin, but I think that doesn't affect it, I think it's Teru-k or Navetsea, who are geniuses in skin tones..

No, sims aren't assigned random skintone genetics.

I've had that exact same thing happen with a geneticized skin that I hadn't given to any of my sims (who only had default replacement skins at the time, and started out as EAxis sims, with no other skin involvement), so yes, it can happen if you have geneticized skins that fall into the range of the parents. That's what geneticized skins are meant to do (they're basically acting as extra "default" skins - it's the whole point of geneticizing/towiefying skins).

If both parents have EA skins (or default replacements) or geneticized skins, these can show up within the range of the parents. Potentially also within the range of the mix of "recessive gene" skin genetics that isn't showing up in their parents' genetics.

I'd think that it's likely either at least one of the parents has a darker recessive gene for the skin and the kid inherited a skin on the range between this and the other parent's skin, or that particular skin has the "wrong" value compared to the other skins you have in your game for it to be on a light to dark scale, so the game picks it up from the wrong range.

(Regular custom non-geneticized, non-towniefied skins won't work like this).

In normal gameplay, there aren't "recessive skin genetics" unless one of the skintones is the alien skin (or a non-geneticized custom skin). There are some "clean" templates where the creator erroneously gave premades multiple different non-alien skintone genes, but that is not normally meant to happen and doesn't occur in normal gameplay.