There is a tool for creating random users and OU's which should then be imported into the CMDB, but as far as I know, not for inventory detail - just too much detail there to generate and you want to associate with computers that are randomly generated also which makes that doubly hard due to the connections
I'll happily stand corrected by anyone that has a tool but it's not known to me of immediate colleagues.
Having said that, this would be a useful thing to have, but bringing up a few VM's is fairly easy to anyone with an established lab and you quickly get a lot of detail in the CMDB.