Well the thing is, Artistic nudity is ok. And in this case, the nudity isn't seeming to artistic... its seeming more pornographic. Examples of artistic nudity are in a couple famous paintings.
It needs more work, no doubt, but it's definitely of enough quality to get into the gallery.
However, I know where you're coming from. Most people seem to swoon over pieces with nudity. 
I was not trying to be offensive or pick on your piece. I have just noticed that many boob pics get approved and to me they seem to need revision.
I like the shading and the lines of her buttocks, seems very realistic. I also like the way her hand/fingers are, you did a good job. I do think her head is too small, and the left arm is either too jagged or outline color too dark... I thought she had dreadlocks so I wasn't concerned about the texture of her hair. Again, I aopolgize if I offended, I am a serious newbie here so... it's cool to tell me to take a hike.
Hey this is nice, i like the budonka-donk. I think the problem with the hair is the overall shape of it, it is too aligned with the rear arm, it is a little difficult to tell them apart by their shape alone. Plus, the hair on her left is short up front, we can see it coming around, but there is nothing similar on her right side, only one short little patch, then the long stuff in back.
Now that I look at it, I can see one section where the hair curves inwards at her neck, but then there is some perfectly straight hair behind it. This section here is visually confusing, and I'm pretty sure it will be completly cleared up if you eliminate the part outside of the curved part. Sorry if I'm not clear.
Also, NotLikeTheOthers, I think your objectivity is compromised. This piece is obviously of high enough quality to get in the gallery, by a very large margin.
The hair is a bit over done. It started good, but I lost it somewhere. Maybe I'll give it another go. As for the face being small, yeah maybe a bit, but not much. She's not a really thin girl, hence the big butt. I'll see what I can do. I find with pieces like this just a few pixels can make a big difference.
Being more realistic than anime style, it tough to get it to look right.
Thanks for all the comments. 
just because people draw naked girls they're art gets approved without needing revision?
I can't see the ref. Face is too small.. Hair is rendered in a pillow shady way. Some parts are jaggy and messy. I'd say "keep up the good work" but its not good. I can't say just "keep it up" because of the context so I'll just say: "go anatomy studies!".
You should refine this piece a little more. The shading looks very jaggy and crude, see the dark shade on her hips below her arm...
thats totally your video, kay: http://www.youtube.com/watch?v=NF9QI18-Bpo
Ref. was deleted. Most likely because the website you used wouldn't allow for nude images.
very sexy, I like the booty