I know there aren't any badges related to tag wikis at the moment so I thought I might suggest a few.
Proofer - First minor edit to a tag wiki.
Bronze badge, awarded the first time you make a small edit to any tag wiki.
Professor - created your first tag wiki with more than x words.
As time goes on and more and more wikis are created, these badges should be fairly rare so it might be worth making them silver. More than x words stops people from writing a single line in a tag wiki to get the badge. Share the knowledge, people!
And possibly a third,
Archivist - created a tag wiki that remained unedited for 90 days.
To encourage (and reward) adding as much information as you can when creating a tag wiki, as well as spell-checking before submission. Obvious flaw: Proofer and Archivist conflict a little, users might make any minor edit to a "perfect" tag wiki in order to get the bronze badge.
Discuss. Perhaps suggest some better names.