Pretty good work in terms how you portrayed her figure - it looks sizable enough, not mentioning sucessful hiding the 3/4 of legs beyond the artwork itself. Bra on girl's body is also fitting well without hiding all the beauty of her body, covered by nothing. Vine-like tattoo among with horns adds some mystic to her. Anyway, it is important to mention about lights and shadows you used - you did very good work with them, plus light places are pretty good in places they are situated.
About backround... I guess you could also use a bit of shadows and lights here, or, in other words - more of them. But anyway work in overall is great and about rating - it is just own opinion of criterias.