Nice pose! I like the way she's sitting. Everything about it seems great, but the wrist--it's too thin. Don't be afraid to add a little bit of bone structure, even for simplified anime! Same for the elbow. :) The colors you chose are very nice. You just need some highlights and shading now--Just keep these colors as base colors, and add some lighter ones for highlights, and darker ones for shadows. That will add depth and 3D-ness to your images. A generic background will do for an image like this--even simple geometric shapes will add to this. I really love the eyes in this one--they've got great expression. :)