Honestly rather poor.
Looks really messy, without much thought put into it, nothing really fits together, the city - all black, in front of a weird water-y texture, which if I recall correctly is in photoshop from stock anyway and the odd brush behind a fish with a unnecessary filter, actually the whole thing is weirdly filtered and it's poorly positioned without you having thought much about it - that's what I'm getting from this picture honestly.
Inform yourself about some techniques people use when they create wallpapers or art in general like en.wikipedia.org/wiki/Rule_of_…
and you'll improve. If you're really interested in this sort of thing then you'll quickly get better and hopefully you'll create good wallpapers in no time!