I just found the model IDs for them on my test antrix server (I have 2 clients) and I thought some people would find them useful.

21659-21666 - Band Characters (Only a Few of the IDs are them)
21667-21684 - Darkmoon Faire Costumes on all Races (Includes high elves)
21723 - Murloc Costume

And here's the 2 Illidan Forms

21322 - Demon Form Illidan
21526 - Illidan

The first number is the model id.

EDIT: Just to be more specific on the band thing...

21666 - Blood Elf with Guitar
21665 - Singing Orc
21662 - Troll with Guitar
21661 - L70ETC (Level 70 Elite Tauren Chieftain) on Drums
21659 - Undead with Guitar

NOTE: For best viewing result please get rid of all weapons before entering the morph id.

EDIT: Added Troll with Guitar to band list.

EDIT 2: Added the darkmoon faire models (not specific).