I would work on the bg more than anything in the wallpaper. It is a bit plain and it is also hard to tell what the bg exactly is. You want to add something in the bg whether it is stock photos or brushes. It would be too hard to tell you what specific brush to use since its more of a feeling but thats what you should work on first. Then, I would add some render effects which you can find in our tut section. I believe Pinoy posted it. Also try to make your wallpaper fit the whole desktop whether it is 800x600 or 1024x800, etc.