The Bungie Halo games have some sick music themes that would be great to try and replicate.
Also the Age of Empires II OST is amazing, both the DLC's and the base game. Just like the spinoff Age of Mytologhy.
However, when I noticed you placed Doom I went nuts, wanna try it out!!!
Viewing post in Future Themes for Jam Suggestion Thread
I went ahead an listened to both, not too much of Bungie Halo games (will need to research more), but I will go ahead and add it to the list. I've also listened to AoEII's soundtrack (but just the original 1999 one, I'll have to research more about DLC and definitive edition), and It seems like a good choice for a pre/early-2000 PC game midi soundtracks (with a nice amount of harpsichord). Also, for future themes I will be using a random wheel for selection, but DOOM should have a pretty high weight (because of its unique genre mostly; music genres that are similar to each latest jam will be temporarily excluded/lowered in weight in the selection process, so there's a good chance it will be selected)