[SixOfSpades]

I do it all the time--one of my favorite combinations is Thief/Mage, whether Dual or Multi, and the annoying thing about combining classes is that you are forced to have the Appearance of whichever class has more hitpoints. So, even though I use my Mage/Thief primarily as a Mage, and Mages look so much cooler, the game wants my to look like a Thief. Not so! say I.
And Elven Clerics look WAAAY cooler than Human ones. Love those spiky shoulder plates.....

There are even ways to make your character look like, say, an Ogre, or Tethtoril, but these are much trickier to implement (to the best of my knowledge, anyway).