Just messing around with a 1px brush... I never called myself a pixel artist but been playing around with it a lot recently. Gives lots of flexibility when you are forced to use the same sprites in different screen resolutions like android mobile. I think I figured pixel art should be about limiting yourself to a certain size. Something around 50px or 24x seems to be ideal. Also different shades of colours can be used instead of black lines but I like the cartoonish feel the lines give.