Altering a prop

[rybray]

For my custom story I would like to create my own paintings. But honestly the tutorials on the wiki are very hard to follow and thrust you into the action immediately and it seems like there are always issues people have between actually making the model and then using it in the editor. What I plan (and I hope its possible) is to take the model of one or two of the paintings in the editor and just, change the picture area to something else. I'm not quite sure if it is possible though. Of course after this is done I'd like to be able to use it in the editor.

What exactly need be done for this to work? What programs should I use?