I'm going to have to say, start over:/
Usually I try and give advice on how to improve the work but this just doesn't work.. Maybe find a better render of Sora too because the clipping around the hair is bad. It's just too intense of a color too, no depth either... it's what I call a "still pic", there's no flow or direction.. just looks like a render on top of a pattern.
For a signature I'd suggest using 100x400 for your dimensions, it looks best I think.