What names are not taken on imvu

There is no list of names that aren't taken but if you don't have an account and you are trying to create one, just keep entering user names until one works.
If you do have an account and you are trying to change your user name you can buy a name change token here
http://www.imvu.com/store/store_us.php

To see which names are available to purchase after you have a token just type your desired screen name in the box on this page
http://www.imvu.com/shop/avatarnames/
This will show you if the screen name is available for purchase with Name Change token or for a certain amount of credits. Usually between 100,000 and 500,000 credits. Much cheaper to find a name that is available with the token.