For your second signature it is not that bad, you positioned the character well, and you have half decent lighting, though there should be more shadows thrown. Your render looks blurry, yet I know the stock, and its a very good quality image, you should make sure you use good quality stocks, and you do not distort them when placing them in the signature, and never ever ever size something up, and it is sometimes a good idea to sharpen the image afterwards, though you should be careful of oversharpening. Its very monochromatic, but in a very flat way, I would try give it a bit more color. The effects are sort of overdone; try reducing the opacity on the wave effect you did. Also, when you are doing effects with motion like that, it provides you with an easy way to give visual movement to the piece - make the effects move in a certain direction, in reasonable relation to the focal. Keep at it, look at tutorials (I know it sounds like something that is just a stock response, but tutorials are very useful at times, and most people I know use them, or have used them in the past.) and you could do well.
Thanks. I have no idea how to throw in shadows though, ha. I'll have to figure out how to do all that. I used the same render(?) for teh background just with the effects added on them, so the background isn't very creative at all. I'll start looking up some tutorials and getting familiar with the program, though. Thanks you!
What I meant by shadows is that while there are brighter parts, there are not many darker areas where the light would not reach as much.