I gotta say your current blows these two out of the water. The top:
The fractals are nice but you need to overlap them ontop of the render to blend him in a bit. Also i reccomend changing the colors next time to make them match the sig.
The depth is pretty nice in that one though, no lack there whatsoever.

Second sig:
erm this one seems almost painted...Like in paint. i don't kow what you did the the BG to give it that look, maybe too much contrast but you need to get rid of it.
Overall it's just pretty distracting that way and there really isn't a lot of flow going on. Keep working at it.