Oh boy.
Y'know, i usually list what's wrong and how to improve...but i'm sure you can criticize your work well enough to know what's wrong.
Just, keep it simple.
Whenever i look at your sigs it feels you proceed this way:
1) place a render.
2) put a background.
3) somebody comes next to you with a rifle and yells you to add more stuff quickly or he'll shoot.
4) you panic, add anything your mouse comes across, add the most effects you can.
5) the man forces you to upload it, after you do that he destroys the .xcf/.psd so you can't fix it, then he flings himself out of the window and disappears.
Just...try to go for a simple and neat style rather than a "put all the filters" one.