Well here we go, not bad for a first try. There's a few rules you should follow when making sigs, which coincide with photography. So I guess it works here.
The first is placement, you want your design to look good but, in my opinion, you should follow the rule where you divide by 9:
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and then you try and put the main object in one of the squares or on one of the intersections - just a tip.
Your picture is a too dark. The background is obvs coloured but too dark. The object, which I'm guessing is Megatron?, is barely visible. I'm guessing you have him layered under a part of the background? You might want to pull it to the front behind the text to make it clearer. (If you want patterns etc over it, then you can just lower the opacity setting:
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Fiddle about with it til you find something you like.
Other than that, keep practicing! Watch
youtube videos for basic know how!
Can't wait to see what else you come up with!