I think gameboys have more ventish things in that lower right hand corner. There are also a couple of stray white pixels there too.
It looks like you drew the buttons with the circle tool, which is generally a no-no (The buttons don't really look realistic either, as the way they are shaded is like a gradient- far to many colours in that purple range.)
Oh. I just put this into paint to see how many colours were used and found that there are heaps of almost identical grey colours - the final colour count for this piece is 134. What program did you make this in?