To be fairly honest, they basic drawing is solid but it's bare on details. Certain details are a bit too thick; both of these combined give the drawing a bit more of a cartoonish look than it needs to be. The color scheme you've chosen isn't helping things either.
Compare those drawings to this (yes tooting my own horn again):
But either way, look at what you can already do if you took all the time you spent worrying about AUs and put them into drawing (or, hell, I dunno, reading, or even watching TV or surfing the 'net) instead.