@The appeal: The guidelines ban self-uploads. You aren't allowed to upload your own art.
Even if that weren't the case, the moderators have the authority to deny something just because they don't like it.
From the words of the Guidelines themselves:

Uploading One's Own Art is Sacrilege

Posting one's own art is severely looked down upon, and there are two reasons behind this:

Firstly, artists tend to be biased when it comes to judging the quality of their own work. What looks good to you may be regarded as mediocre to Danbooru moderators.
Secondly, allowing posting of own work (self-posting) will cause a sudden spike of sub-par uploads as users mistake us for another Pixiv or Deviantart, far beyond the scope and capacity of Danbooru.

More suitable sites to upload your own art to include Deviantart and Pixiv.

Admins and moderators are especially harsh on self-posting artists, lashing out penalties without remorse. The one and only way to feature your art on Danbooru is to show immense talent and skill elsewhere, and with that, captivate some fans on the other side of the Internet into uploading your art.