Self Artwork: You can upload your own artwork but be aware that Danbooru is not a place to expect positive reinforcement. Your uploads will be subject to the same standards as everything else and may be flagged, downvoted, or even deleted. If you don't want to risk experiencing these things then don't upload your art.
It's in Danbooru's TOS.
...that's entirely irrelevant to what he was asking. Unfortunately I don't dabble much in the workings of artist entries, so I can't be of much help.