My own personal rule of thumb when posting pics:

I once used to post pictures here and felt guilty about it later because I felt since they were not mine I shouldn't post them. However, I made the exception (for the pictures below) because I found them on IMDB and I felt that is such a public arena I'm not stealing them really from anyone. They are pretty much, in my opinion there for the taking.
If there are pictures I want to point to on other sites, I'll link them.