Let me also add this link since it looks informative for anyone wanting to hack the VSM file format...
http://www.blackberry.com/developers.../Branding.html
It explains the various resource_types which may (presumably) appear in the VSM file. My guess is that the resource_type identifiers will appear in part of the header/unknown bytes in the VSM file.
(Thanks to user hhardheart for posting this link previously).