Most of your things look pretty nice, but a lot of it is very simple which could be improved. Worst of all in my opinion is this:
All you did there was pretty much open a canvas size, put the wallpaper in and add some patterns. The quality of it is also very low. But from what I can see, you probably posted these from old to new so it's nothing to complain a lot about. Another example of simplicity is this:
Don't get me wrong, the simplicity looks nice to some extent, but nothing to be impressed by. So there could be improvements. Mostly I think you should try using C4Ds and fractals a bit more and try different ways of using them because them being used in the right way can look very nice.
So, some of these look very nice but some of them are too simplistic for my liking, so I think your signatures would start to look even better if you practiced a bit more with C4Ds and fractals.