From what I saw in the dumptruck_ds review, the Prototype WAD is really cool, but I feel it could also have some "prototype decoration" textures for things like trims, doors, arches and so on. This way it could be useful not only for mappers, but also for people wanting to create fully featured texture sets. 

Why would you be fiddling around with decorative details during the prototype pass? 

Because I started to create a fully original texture set, and when making a map for it I started realizing all kinds of details that are missing. I've also realized that the texture dimensions of such details needs to be standardized, otherwise the geometry and texture alignment will need lots of adjustments when iterating through textures.

There's also the question of when to create details using generic textures across tailored geometry, and when to create details using tailored textures on generic geometry. A set of prototype decorations could be a guide for that.