Pictures aren't used in making decisions per se, but some colleges/universities like to have them to remind them that they're dealing with people on the admissions. None of the grad schools I've looked at ask for pics, but when I was an undergrad, I sent loads of photos with my applications. Smaller colleges often publish a pictorial directory of the freshman class with everyone's pictures (as submitted). It wouldn't surprise me that this grad school does something similar, so be careful in picture selection... (my undergrad photo had me in a pinstripe suit, black shirt, white tie... kind of mafioso looking. It got cropped right below the knot of the tie for the freshman lookbook and I ended up looking clerical instead).