Hey, you're off to a fine start. First and foremost, keep it up.
A 'problem' (as I call it) that a lot of rookie designers run into is the feeling to need to include a player in their entirety into their sigs. As you can see, they turn out tiny. Now, maybe you specifically wanted his entire body in, but I recommend for the future trying different things.
For various backgrounds, try out http://www.good-tutorials.com
and search through some effects and how to use various filters. You'll learn fast that by simply playing around you can figure out what does what, and what seems to work for you. You can search everything there, from text effects to image effects to what equates to background effects.
Beyond that, just keep it up. Practice is the best teacher, along with experimentation and doing things outside of your comfort zone.
The cutout looks good to me, but it's so small it's hard to judge. Though, as I said, I don't see anything wrong with it. Looks well done. What method did you use? Zoom with the erase tool?? Polyagonal lasso??