Click on the "Profile" button at the top, then click on the "Forum profile information" link. You can choose another picture there. You can't upload your own unless you are ranked as an expert (or maybe contributor, I don't remember now). To get up to 3 normal stars, you just participate in the forums and when you've been around long enough, posting enough messages, you'll get more stars. People with special stars get them by demonstrating their expertise or contributing a game (if I've missed anyone, BTW, let me know). The special ranks are "Contributor" (2 special green stars) for those who have submitted games, "Clever" (3 special green stars) for people who help others out with clever advice, "Expert" (5 special green stars) for people who have demonstrated mastery of SGDK, understanding of all its areas and ability to use them in interesting ways (...and for the administrator's girlfriend
... who's doing pretty will with SGDK2 herself), and finally "Administrator" (5 special brown stars).
