Wait... Isn't there already a
thread for this?
Edit: The sigs aren't too bad btw. The thing you need to work on imo is making the render blend well with the background
*. A good way to do this is after you find the place you want the render, /place a bigger copy of it and blur it until you can't tell that it's the same render anymore. That way you already have a good color scheme that goes hand in hand with your render because technically it's all from the same source image. Then from there you can blend/add text/add effects/etc. as you wish.
Also, if you can get adding text down your sigs will look so much better. This includes making sure the text is the right color (not always white all the time), a good font (Calibri and Arial are far superior to any other fonts and will literally go well with any type of sig if done right), and good placement (this you don't have to worry about so much at the moment, once you start blending your renders so they flow then you can worry about good text placement, but for now sticking it in the corner will suffice).
*If you look at your Cegapus sig, the render looks like it was added in last and does not look like part of the sig at all. It seems as if you used as few as 5 layers for that one (or 4 if that's a pre-made background).