Very good for a starter, you have a grasp of the basic structure of a sig, but this is definitely not enough to please the high standards of TBT. Look at some tuts, get some better renders, and try to incorporate your renders with the background a little more (rather than putting them in front of a fractal render or whatever that is). In my sigs I like to start with a gradient in the background, then work my way up through multiple layers, and add a few C4d renders here and there (C4ds are very useful too). Another tip, try playing around with the layer modes, it helps blend your sig together a lot I've found. The best way to get better is to practice, and play around with things until you get a satisfying conclusion. But over all this is a good start!
Here's my first sig (I did have some Gimp experience prior to this btw)