JP LeBreton has recently announced the "DECK" (Doom Engine Creator's Kit) project, an open-source public-domain all-in-one bundle of Doom technology: a game engine + editor + game assets + tutorials, all integrated together and easily accessible. It's intended to empower people to easily make cool lo-fi 3D first person games and it sounds really cool...
... but it needs help. It needs some Doom-style character sprites, some Doom-style environment textures / decoration sprites, and a lot of audio design. Pitch in and help build free indie game tools!
Here's my contribution so far, some painterly-ish pseudo-photo "medieval manor" textures:
It was kind of fun to work at low resolution without having to worry about shaders or 3D meshes or UVs or whatever. I recommend it.