>>9
The only real problem I see are the spelling mistakes. All other problems you named can be solved if the developer does some thinking. Have a look at danbooru (http://danbooru.donmai.us/ blah blah warning very very NSFW) for how a properly designed tagging system can work.

• It solves such things as plurals and different names for the same thing with aliases and implications (for example, "inumimi" is aliased to "dog ears").
• It allows all users to quickly correct tagging errors and to add or remove tags in a wiki-like fashion and also keeps a history for quick rollbacks in case of vandalism.
• It uses tag suggestions to help users decide how to properly tag things.
• It has a page with an easyly understandable explanation of how tagging is supposed to be done and what conventions there are.
• It allows you to easily search for pictures in a way that would be hard to do without tags (For example I could search for images that are tagged inumimi OR nekomimi but NOT loli and NOT shota).