Heres 2 new ones.
http://img391.imageshack.us/img391/6...dorisigef0.jpg
http://img75.imageshack.us/img75/5551/grimjokk2.jpg
Printable View
The TimeShift one has too much blending, try getting rid of some of it. Try blurring the C4D's in the background some as well. It needs a LOT of depth. Your focal point is a little over-sharpened. Your light source is like a solid block, try using a 200px soft brush on about 20-30% opacity and click 1 or 2 times where you want your light source to be.
Both are a bit over-contrasted, maybe make there be less light because it's a bit bright. :D Move the text away from the corner on the first one and change the font to a sans-serif and a bit smaller. No gradient map on it. :D
For the second, the text is good because it fits with the render.
Get some more depth by getting a stock background and blurring that, and sharpening the render. Read some tuts, from Papa, Garis, Immortal, Soggy, Elramo, and others. :P
Good luck with learning!