Yep, Matts tut is the best.
Riquelme; First thing i notice, No text. No text can be fine but the right hand side is soooooo empty so text would be nice. Dont like the black splatters on the right side. Good render effects though.
Torres; Superb! I love it, Great brushes behind the bg lines.
Dont like the lines up the top and bottom which go over his head. The text is alright but overall great sig.
Kaka; Nice bg, Looks a bit plain, maybe a sparkle brush or a light grunge brsuh would be good, whack on a border, add some text and muck around with different render effects and that sig will all of a sudden be so much better.