It takes guts to post in the design area when you first start. I commend you for that! You have some way to go. Personally out of the three your second is my favorite. The background on the third seems blurred,and simple. Try to stay away from using that much of an outer glow(or whatever effect it is) on the render. The render looks like it has been stretched, but then again im only a bystander and dont make sigs. I would recommend hanging out with one of the gimp users on the team and learning from them.