One thing I'm noticing about all your banners is that the render doesn't quite blend in with the background... at all. @_@ As somebody else has already said, it looks as though you're just making a background, C+P-ing your renders onto the canvas, and applying an outer glow layer style. First of all; outer glow = no. If there's one thing I've learned regarding GFX, it's that outer glow NEVER works... with anything. It seems like it would be a cool effect, right? Wrong, it's not. Especially when there's so many other techniques you could use to achieve the desired effect (such as smudging on a different layer type, etc). Second of all, the render should be one of the first things in place. That way you avoid the "this-was-slapped-on-in-the-last-minute" look, if you know what I mean. Not to mention having the render in place when you start helps you design the background around it.
Another thing I'd like to comment on is your use of text. Don't use gradients when it comes to text. Period. Also, having the text the same color as the background isn't exactly a great thing to do (most of the time). In my opinion, text should sort of stand out. Usually you can get away with plain white, but sometimes you need fool around with it to find the right color. I usually consult a color wheel, just so I know which color is complimentary to the background so I can work off of that.
Y'know what? Here; I want you to read up on
color theory. I know it might sound boring, but I really think you could benefit from it. In my opinion, it looks like you already know how to use Photoshop. It's just the elements of design you need to familiarize yourself with. Also, check out a few tutorials on dA. Tutorials are really helpful when it comes to picking up new techniques.
Anyway, I could get into depth, lighting, focals, space and all of those boring things, but I'm sure you've heard it all before. Like I said, look up some basic elements of design on google or something. I'm sure you'll find them useful sooner or later.
