I just released a set of scripts that come in handing when creating clean images for virtual environment, heck you can even use it for cloud images.

What they do is:

• clear all the logs
• clean up the networking scripts, because the normally get references to the mac address in CentOS
• clean up the repository files
• in some cases create a root user

There are scripts for: CentOS 6, Debian and OpenSuse.

They can be be found in the tools section or in github.