I think I've decided I'm going to build something in EGA specifically (for that colour palette), and write everything in C on Watcom's compiler most likely. I'm hoping it'll run at a decent enough speed on a 486. I'm thinking something along the lines of the 1991-1992 era blocky platformers like Duke Nukem, Cosmo, etc.
That being said, part of me wants to go full LucasArts, part of me wants to write a wolf3d style raycaster....