create a face

i've been playing around with updating bullsfan's 06-07 roster. i'm not sure how you update ratings (i know how to do it, but don't know how to determine the values accurately), but i've been working on rookie faces. i've found a lot of pix of the rookies, i've enlarged them with irfanview and loaded them into data/users/faces, but when i go into the game, to create a player, and load image, only a few of the photos are there. the photos are all jpegs's, about the same size but i can't figure why some work and some don't. any ideas?
thanks,

stratjim