Wow, quite a lot of stuff on display here. Plus, I really like your work so far and I can sense a lot of hidden potential here. :DD
If I had to pick my fave, I'd go with this:
http://i1295.photobucket.com/albums/b625/bennypoop805/BlackOps2_zps32713976.png
This piece avoids looking as monotonous as the rest. And I really like how you've successfully blended him in the background and it looks so natural. You have smudged a bit too, right? It shows. lD The only major flaw I can see in here is the text. Doesn't quite fit in there. Although, admittedly, it is still better than all the other works where the text just looked tacked on because the font style didn't match the contents of the tag. Here, the font and stuff is alright, but positioning is irksome. I'd advise you to expand your canvas size a bit so that text doesn't become a problem. It becomes increasingly difficult to add text in narrow tags. As it stands now, I can't suggest a perfect place for text to be placed in that tag. Also, the lighting is a little heavy on "Duty"'s 'y'. :p
Another problem I see with your works is that you tend to, at times, work with low quality images. Never do that. It really undermines all your hard work if the quality of the stock spoils the whole tag.
This and
this piece really look bad due to the render/stock quality, really. Some of your tags are a little monotone too. When you go for monotone, depth is needed. But your tags can't seem to pull of monotone look. So yeah, go for different colors, I'd say. And spam selective colors like I do! lol This is all my opinion, though. So don't feel bad if you feel I'm trying to undermine your hard-work or something because that's not what my aim is. I speak what I think and I really wanna see you improve a lot as a graphic artist. <3;
Seriously though, some really good work here. I can see you go places. :]
Edit: In
this one, I can see you went overboard with a gradient map or contrast. It looks a little choppy and lighting is all over the place. Some parts of the render are totally dark while some are really bright. If you try to keep stuff like this in check you'll end up with better stuff, imo.