The Pre-Fab Four
The Stepmamas and Papas
Panic at a Neighboring Disco
The Pretend Pretenders
In a Rush Tribute Band
Wow. That's a lot harder than it looks. Here are some real ones that are pretty amazing:
The Faux Fighters
Short Answer: I think there is a lot of humour to be mined if you already know the band in question. (Example: You know it's Grapes of Wrath, so you call your band a different Steinbeck book. Cannery Row, perhaps?) Also, taking references from a band's albums and songs makes for good tribute names. Like, Life On Mars as a Bowie act, or Never Say Die for Sabbath.
Note: I've got a friend who's in the best Aerosmith tribute band that ever existed. It's called Aerosmith Rocks. http://www.aerosmithtributeband.com/ Worth the price of admission, methinks.