I disagree; it's not refined enough to be submitted. I suggesting finding something else for your background - try
working with textures and brushes, or even find other scans and placing the character in an appropriate
environment/setting.
Also, the character in full opacity - while the scan isn't in bad quality, the extraction needs some work. Try
looking up tutorials on more effectively extracting images, and look out for jagged lines, there's many on the
scan. This would look a lot better with crisp lines.
I might've pointed out a few things, but with a determination and extra work, this'll turn into a greater
wallpaper. One last thing, it would be very helpful if along the way you posted
links to the pictures/resources that you utilize. :)
Good luck!