You can actually post any type of the photo of yours. However, it is not recommended to use the nude pics, as they can serve as a sign of something negative. if you want to share your nude pics, you’d better do it via the private messages. Or some of the sites have settings like private and public photos. You can upload the nude photos of yours but making them private. It will allow you sharing them only with the persons who you want to see them or if they were requested. In other words, don’t forget about your security.