Sup alister, cool drawing. If you really want some solid advice on this check this page out:http://conceptart.org/forums/forumdisplay.php?f=59Lots of pros on their to steer you the right way and very cool advice and comments in general.
I know nothing about drawing Ali, but if you could somehow give her shades some sheen in the way a lot of trendy shades are, it would probably add some contrast to your picture.
0A0 awsome website!!
Awesome Alister!!! :D Ha!