http://img521.imageshack.us/img521/2849/timeshiftbestandlongestys0.png
http://img521.imageshack.us/img521/5128/cabalcz3.png
http://img242.imageshack.us/img242/9099/dmcdante4pb2.jpg
http://img152.imageshack.us/img152/425/gwstockgz4.jpg
http://img515.imageshack.us/img515/9164/ironmansephiatonedk3.jpg
http://img515.imageshack.us/img515/4888/lineage2stockbh3.jpg
http://img515.imageshack.us/img515/4294/metroidwithflowna8.jpg
http://img295.imageshack.us/img295/6323/bowsersigno2.jpg
http://img108.imageshack.us/img108/6707/ichigovgcatsenhancedligaa3.jpg
http://img164.imageshack.us/img164/3221/linktagvb9.jpg
http://img186.imageshack.us/img186/9440/spiderboymoreyellowrt7.jpg
http://img108.imageshack.us/img108/1889/spritenormalcolorsbd5.jpg
http://img116.imageshack.us/img116/4760/haseo2normalcolorstj4.jpg (http://imageshack.us)

bump bump
bump

Some of them are nice but most of them have a handfull of faults.

1. Most of them are wayyyy over sharpened and are over contrasted.
2. Poor light sources, and most are way too dark. You should experiment with the dodge/burn tool.
3.Way too chaotic.
4. You should use less of the same effects and try using different kinds of effects and work on the text.

Yea, a lot of them are over sharpened. But the Time Shift one is very nice, and I also really like the Bowser one.

most of them made my eyes hurt >.>. the first one is good though

What Runahs said made a lot of sense, other than that you need to work on blending your renders better with the background. The first one stands out the most to me as well.

Timeshift is the only decent one.
Too many faults.
No control in the sig, you just planted abstracts over and over as if you didn't care how it looked.

1st one is good.
2nd one seems like it doesn't blend and it has too much going on in the background.
3rd one could've been good if that 2nd Dante head was gone.
4th one seems like theres to much happening on the right to be blended with the left.
5th one needs some action on the right side.
6th one doesn't seem to work at all, no real blending, and that extra face.
7th one doesn't blend also. The work on the right side looks better.
8th one is good, but could've been better.
9th one seems to bland.
10th one is ok, but the greenish/blackish background sorta messed it up.
11th one is actually pretty great. But the blue, purple, and green messed it up.
12th one is fine.

They're all really good, but like Runahs said, over sharpened.

But even with thaty, they still look good, especially the first one.