I went back to see your tumblr page where you have your deleted artwork (I was mostly looking at Sokka though ). I read up on the deviantart policies and it says that nudity is allowed as long as it's not displayed in a pornagraphic manner and/or underage. Since the picture does not contain any of the criteria considered pornographic listed here [link] then the issue must be with the age of the model. Again I bring up the issue that the avatar world is like a historic version of our own where laws back then were different from those now. Although this should not be an issue now because we have officially seen Sokka portrayed as an older man so the age of the model is irrelivant which means the artwork can be reposted.
...yep this sounds like a justified arguement for getting at least one of your pictures back.