The big logo isn't bad but everything else is.
There is way to much blank space.
the items seem to be randomly placed.
For a good design you want to try to keep the viewer's eye from wondering too much.

One thing that really pisses me off is the signature.
Your signature is very visible and takes a way from the main focus of the banner.
The signature should be somewhat hidden where is isn't distracting, but the viewer can find it if they want to.

Also the banner is nowhere near being balanced. Everything is mostly in the bottom part of the banner.

That is what came to mind as soon as I looked at this banner, there is definitely a lot more that could be fixed, but I'm tired of typing.

I know nothing about this clan, but I am going to assume that is their logo and you did not make it.
That being said, this is not that good.

For starters, I am going to say what I notice right after looking at it:

The Logo
You used the clan's logo way too much in this piece (10 times). Cut down on the usage of the logo, because it looks like you just copy and pasted it everywhere, and this does not make an image look good. The silver logo in the middle has way too much inner shadow/glow. Try toning it down so that almost entire parts of the letter are not filled with white. The lightning also looks very out of place, and that is because there is almost nothing in this picture. If you were to add stuff to the picture I am sure the lightning could have looked alright at the very least. Fill that blank space up.

The rest of the image
The red at the bottom looks out of place, and placing the red logos over it makes them look out of place too. Try changing the colors of everything at the bottom. Next, you should probably give us something to look at, try adding a background of some sort to the banner. I feel this would greatly improve the piece. Finally, I agree with Critical about your watermark, but I can understand if it would be taken out before they used it. (If not, make it smaller and lower opacity please.)

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That's all I have to say. I hope you take the advice I have given you on your next piece. I can tell you are new to this and I encourage you to keep practicing. Next thing you make send me a PM and I'd love to look at it.

Looks good and simple, I just don't like the fact that the image looks a bit empty.
One other thing is the shadows inside the text just don't look that good in my opinion.

All in all I really like the style, I would've wanted more in the background and a bit more lighting stuff etc.

Keep up the good work!