I'm discussing here and there a trick to assign good keywords to items in a consistent way into any wiki project. The advantage could be, that they could be searched by presently running search engine. I'm working into a couple of wikisource projects, but I presume that the need of a comfortable keyword search is much mandatory into Commons.
Here the links to my contributions:
http://meta.wikimedia.org/wiki/Meta:Babel#Keyword_search
http://en.wikisource.org/wiki/User_talk:Jayvdb#Thoughts_about_keywords
I's like to know your opinion about.
Alex