We had a lot of vms being deployed from template & then being deleted, BUT there were many folders that were empty except for the imcXXXX.tmp so I decided to investigate.
The file imcXXXX.tmp exists after cloning/deploying vm from template and choosing to customize it.
The temp file is created, then after the vm is powered on the file is run inside the vm, customizing it, and the .tmp file in the home folder is removed automatically.
If you never power on the vm but then delete it from disk, that file will still remain in the folder. You have to delete it manually afterwards.
A bit more about cutomization can be found here:
http://communities.vmware.com/thread/299305