The Hawaiians plate comes from Leialoha B., who gave the plate as a Christmas gift to her guildies in Hawaiians on Thaurissian, and the "MPG FTW" (which isn't really WoW-related, unless there's an "MPG" acronym we're not thinking of in the game ("Mana per gallon"?) comes from Angelo. More MPG for the win, indeed. And finally, the ZOMG LOL (also not necessarily WoW-related, but we'll accept it) plate comes from Joejohn, who saw it as he was driving around the other day in Washington, DC.
All awesome. If you've got another plate for us to add in, drop us a note with a picture and we'll get it included.
Gallery: WoW License plates