Does anyone here have experience with Game Extractor?

[gameripper]

I don't know if that will work on DOS games, but thanks for the suggestion anyway.

Yes, it will work. The "-s" scan feature does not care about the platform, it just scans for all known asset formats. Lots of formats are supported, but admittedly not that many from the old DOS era.

Also all detected images will be automatically converted and exported as PNG, so you don't have to worry.

I've at least been able to identify which game files are BMP files, it's possible they could be LBM files though

BMP files start with the bytes "BM", LBM files with the bytes "FORM". The links I provided contain detailed description of each format, with magic bytes (bytes that identify a format or codec are called "magic bytes").

would it be possible to run some of those older programs on a Windows XP or Windows 2000 virtual machine and convert/uncover the files that way?

You misunderstood me. These are all modern programs designed to run on the most up-to-date systems; they just happen to support old asset formats too.

Simply put: they all can be installed on Win10 / Win11 just as-is, no virtual machine needed.