otoko no ko - males who have taken on the appearance and/or identity of the female gender.
shota - art that depicts preadolescent boys. Use this tag only with sexually suggestive or explicit content, otherwise use child.
yaoi - usually involves bishounen and is intended for a female audience, but on aibooru, yaoi is used for any romantic and/or sexual depiction between males.
Remember to only use those tags when at least two characteristics are present. I.e tiger ears + sharp teeth or tiger stripes = tiger boy. Otherwise the one specific tag will suffice.
cow boy - A male dressed as a cow or with cow-like features.
