Wow, way better than my first sig, lol my first is a mess.
As stated before the key too a good sig is focal point. This means one render, so pick one of the three figures in there and erase/delete the rest. (preferabley keep the one in the middle best for composition :P)
You background is looking okay however I think your should work on your coloring.
Color your background a color tat is close to your render will help a lot with blending.

Finally your text is pretty good in size, however the biggest rule when making text is to use DEFAULT fonts , so this means like arial, tahoma?, eurose if you have it.

Nice job on the border though, and the text is actually pretty good, WAY better than my first so your doing well.
I would suggest following some more tutorials, and asking anyone and everyone if you get stuck, need help with something, or just have a question