I don't think that it is possible to use the same image for different domains, because the domain-name is used in other contexts in syspref.inf.

Ie. in the section: params.MS_TCPIP

Example:
code:
[params.MS_TCPIP]
    DNS=Yes
    DNSDomain=YourDomain.com
You could overcome this by make making a ghosted image before using sysprep, and then use a different sysprep.inf for each domain.
Sysprep it, and make a new ghost-image from here.
Reload the not-sysprepped image and make a new image using a different sysprep.inf for the next domain.

This way you can create a different image for each domain.

-Erik