I have a server that is pure vanilla. (Although I might add anti-grief soon). The whole idea behind this server is to build a city in each biome, however, in each biome there will be specific types of homes you can build.
For example, in the desert biome you can only build underground homes, the mountain biomes you can only build homes inside the mountain, etc.
In the flatlands biome, its a free-for-all and you can build any building you want, as it is spawn and will serve as a type of community housing/material type of place.
This server is open 24/7 but I will be having whitelist on. If you guys have any suggestions or are interested please let me know :). The idea will come into fruition either way as I'm still planning to do a cities/homes in biomes, but it would be cool to have other people's builds in the server.