Ehm... hmm..

I really don't know what to think.

I feel like you're half trying to emulate the style of other people who make really good tags, and you're half trying to create your own style, but something about the renders always looks totally completely off.

At first glance I think "Wow these are sexy", second glance "Wait are these the same sigs?", then after a couple minutes of looking close "Oh..."

You have a good -look- down, you just need to master the details, because the details feel really, really sloppy.
The first one, the render looks very second-thought and oddly blended. I strongly dislike it due to that.
The second one is the best of the top three, imo. There are less sloppy aspects, but it still looks a bit messy.
Third is good, except the blue C4D effect render looks -very- bad. Like you put it in and set it to color dodge and that was that, it looks too... grossly contrasted? Or something.

4th is actually the best in my opinion, from a technical standpoint. You edited yourself and didn't add too much, none of it looks too sloppy except maybe the pentool (using a big, hard round brush like that can look juvenile, try doing the same thing but with pencil maybe?) and the composition is nicer.