What exactly have you've done on these edits? It would help a lot to understand what exactly you have done and so forth.
Otherwise, here's what I can offer as a critique from just looking at them;
First image: The only thing that sticks out to me is how her hair was edited. I can tell right off the bat that you feathered it. Editing around hair is difficult- totally understandable. I would have also adjusted the photo of the girl and try to sharpen it. Maybe even try to darken her a little? Not sure, exactly, but I would definitely play around with the contrast and such. The background on another hand, is awesome. Definitely a keeper.
Second Image: Looks good. I'm just not sure what it's for... is it a wallpaper for a desktop?
Third Image: Same as before. But I think it would be cool if you texture it. At least to see how it would change it. Also, I'm not really digging the background. It just doesn't stick to me- kind of makes me feel like I should skip it just to see what else you have. The style of the background clashes with the style of the emblem in the center.
Fourth Image: Looks like you're playing around with texturing. I would love to see the finished product as it appears to be heading in an interesting direction.