Sticker-bility Puzzle
The Puzzle: 
The addition sum below is a puzzle I've been trying to solve. The idea is that each type of sticker stands for a different number, but that this number is the same wherever that sticker occurs.
So far I've got it to the picture shown in the second diagram. Can you finish it off for me?
Look again at the diagram:
The only numbers which haven't been used so far are the 0, 6, 7, and 9. The first one to work out is the brick wall, which has to be the 7, since none of the others fit, which means the shaded square is the 9, and the completed puzzle is:
8357 + 792 = 9149.