MyGamerCard have launched a new feature, the
GamerPic Scout, allowing you to browse all the available pictures by keywords and see how popular each one is. For example, Catdafelix is one of only 10 people using his Rumble Roses pic, while Norrec is slightly less unique with 458. The pic I use has 11,114 other users and is the 30th most popular, primarily because it's one of the free ones that the console comes with.
Interestingly, there are a few gamercards without a single user, mostly from games about sports, games that are crap or because they just aren't very good pictures. All in all it's a fairly good resource for people happy to spend money on gamerpics.