Speaks for itself.
One thing Doom had was nice synergistic sets of textures. There are actually three floor textures (or "flats" in Doom terms) on the floor: two different basic stones (but with identical edges so that they can be mixed and matched) and then the one with a grating (also with identical edges). Oh, and then the teleport-gate-rune in the corner (so four).
I made the walls by stacking three normal Doom walls on top of each other (three of the same for the basic wall, and two plain walls with one alien-face wall in the center for the special ones), due to the differences in resolution and aspect ratio. (The window is standard TS2, not Doom.)
Maybe someday I'll actually use them in the game, rather than just
in my little test lot...