Unfortunately there is no prize for completing the picture albums, at least not for the IFs and Wilt ones. I got the earlier pictures by beating the highest score on games that came out last year such as Bloo's Brothers, Cracking Up. Sparky puts a list of mini-games on her website and the lower level ones are probably the ones you want to work on. Check out
http://www.fosters-home.com/houseparty/minigames.htm