From the looks of it, it seems like you outlined the image with the Brush Tool. To me, that probably isn't really a
good tool for the purpose, since it's really unsteady. ^^;; The Pen Tool is probably the best tool for outlining,
but I guess the Polygon Lasso Tools works fine as well if you know how to use it.
Honestly, I can't really give any further advice without a good outline/vector there, since the difference between
a good outline/vector and a bad one could make a big difference to the final result. What you can do for the cut off
part though, is to move the vector to the right side.
So...try practicing how to vector an image a few times. It'll be kinda tiring at first, but once you get familiar
with it, your speed and accuracy will increase, and thus the result would look much more beautiful. ^^ Don't worry
about the wallpaper yet. Just focus on the vector for now. You can't really go anywhere without a good image first.
^^;;
As for how to vector...there should be some tutorials out there (you'll just need to search for it). Don't ask
me. I know how to vector an image, but my method is self-taught. Probably not the best method out there. xD;;
Good idea for the Title though, btw. ^_^b