Fixed themes and alphabetized them.

[MattMadness]

I noticed some new themes had popped up in the last few months and I decided it would be a good idea to alphabetize them, and also fix major and minor issues with some of the themes (i.e. an image not loading, the sidebar in the retro theme entirely reversed and full of whitespace, etc.). I've tested these changes and they seem to be working fine, and I'm open to any recommendations.