Hi, Anybody can tell me what are photo based brushes and image based brushes? as in http://www.andreasrocha.com/gallery/scene_finished/070720exodus.htm "No photos or photo-based brushes were used as it was one of the contest rules" Thanks.

I believe it's just what the name implies. Brushes are just images and it's entirely possible to make photos into brushes. Perhaps reading up on the brush making process will help, there are plenty of tutorials at places like deviantart.com or pixel2life.com. :)