Use the following trick to decorate your house with custom art. Your Sim must have a Creativity level of 5 and be able to paint a still life.
Have your Sim paint, and a frame will appear. Center it on what you want to paint. You can also "paint" something that is not in the game by pressing C to pause the game, then press [Alt] + [Tab] to switch outside the game.
Start a graphics program, such as Windows Paint, then load the original captured in-game picture at "c:\mydocuments\eagames\thesims2\storytelling\snapshot.bmp".
Then, open the picture or image that you want to replace it with, and put in your game. You must resize your custom picture to match the same resolution as the "snapshot.bmp" file.
Copy your custom picture on to the "snapshot.bmp" file, then save it. Press [Alt] + [Tab] to switch back to the game. Your Sim will begin painting your custom picture.
