It's actually pretty good, as a picture/drawing. As a sprite or pixelart, though, it needs some work. Don't get me wrong, the picture is great, but - at the moment, very boring. Especially with large faces like that, you want to put in quite a bit of shading, and I would also suggest making the dark colors lighter to allow for shading as well. Putting a logo on the T-shirt or a letter or something would kinda spice it up a bit as well.
So, the drawing is great, but, in a pixelart form, it's just not spiffy enough, really.