Always wanted to see classic Doom and Hexen with more detailed geometry. I didn't like the way it was (re)done in Classic Doom mod for Doom 3. The way I want to offer is Geometric Textures. Nothing really new indeed, but this feature could be implemented in "non-forced" way, so textures could be "made geometric" one by one on demand and free will.
Idea is simple. Make library of so called Geometric Textures (GT), where every such "texture" consists of LODs of height-mapped polygons and additional decorators and may also be animated (like wavy water, slime, etc.). LODs could be static or dynamic (procedurally mixed), depending on GT source format and used algorithms. Of course, advanced vector/pixel shaders could be used to add even more detail and simplify far LODs. It is known that in Doom walls and floors textures often clipped in different ways (depending on sectors shapes), so GT technology should use some CSG tricks to CLIP AND TIE neightbour edges of two (edge) or three (corner) surfaces in two ways (outward variant and inward variant). This will do the trick and give us more detailed geometry in cost of more polygons and some massive pre-processing.
Also I can do most coding work on this feature, if required.
I hope there are people who also want feature like this, so I'll be happy to know your opinions and suggestions.