I'd suggest taking a good 30 mins and looking around at tutorials. Don't get me wrong your sigs are not bad, they just could use some simple cosmetic photoshoping to turn out alot better. From what i see is your canvas is covers in a fractile brush maybe a picture and some simple text.
What i would suggest is try a wide variety of layers, opacity, different style brushes. Check into text tutorials because believe it or not text can make or break your sig. Without good text the sig could be crap. Also learn some technics for better blending of images.
Belive you me this is in no way a flame or an attempt to put you down. If you looking for constructive critisism then i believe i gave it to you right there. So please take this into cosideration and dont hate me. Thanks
[Sorry for spelling errors!! But you get the picture]