Good work here.
You are pretty good for a beginner (you are a beginner aren't you?). My two complaints are the shading, as the only shadow in this pic is on her neck. I understand that this is a fanart for an older anime (Slayers ftw), but proper shading is important. The other complaint I have is the quality of the picture. I know it was done in MS Paint, but there are plenty of other programs on the web that offer better quality AND are free, too. Might i suggest Paint.net? its a very good quality program, was originally intended for an upgrade for MSPaint, and has a picture quality that rivals Photoshop. Thats all I got.
P.S. I clicked on this onebecause it was Lena. That is as good a reason as any.