Well, Clizz, here are my suggestions.
1) Your shading is, sadly, horrible. Use WAY more shading. As is your pieces are flat blobs of maincolor with a tad of shading thrown on.
2) Use better palettes. You could blend some blue into the shadows of that white and it'd be a thousand times better.
3) Outlines. Sonata already mentioned this one.
4) Learn to selout.
5) Again, SHADE SHADE SHADE - nobody EVER said 'I'm sorry, but you shaded this too much for my taste. I like work to be BLAND and TASTELESS'. Not gonna happen.
I don't have much time, otherwise I'd do a quick edit, but for now just stick with the advice.