I remember seeing an old film on TV when I was really young (it must've been black and white cos it was ancient!) about a picture in a gallery that came to life. The people in the picture were painted all sitting round a large dinner table and came to life at night and sometimes even left the picture. I think someone like Basil Rathbone was in it (yes - it was that old!)
I'd like to find out what it was - has anyone ever seen it??
I don't think it would be. In that, the painting was of just one man, and it was hidden away in an attic gettting uglier and uglier whilst the sitter stayed as beautiful as the day it was painted.
I couldn't say which film Mysticshaz is thinking of, though.
Could it have been the first episode in the film Three Cases of Murder, a British film from 1951 starring Alan Badel? In this episode he was the artist; the picture showed a manor house down a long drive; but the house was full of people, some of whom were not originally there....
However the film you describe sounds as if it might have been a comedy. Try the Internet Movie Database.