For the piece itself, It needs to be something you drew/painted/etc after the topic was announced-- anything after may 18th is fair game. This isn't super-easy to verify, so just be courteous to other entrants with this one.
Concept wise, do anything. You may absolutely revisit an earlier retype, redo something old, re-illustrate an earlier concept, or anything along those lines.
Nobody asked this, but I'll say anyway--
If you do a piece for this thread and decide you want to do something else instead, no problem! You can post as many efforts as you'd like. You can only enter one piece into the poll, though, so just make sure we know which one to put up in the poll thread by the time the deadline rolls around.
Cool stuff being posted so far :) really glad to see all these entries!