As you can see from the image here, your Sims can paint pictures of their own choice (Custom Pictures) and not just the ones Maxis supplied with your game. Full instructions on how to add them into your game is there too.
There’s 459 various images in Set 8 to choose from in the 29.5mb zip file which you can Download Here!

I will add more when I have time to prepare them.

Enjoy. 🙂