Out of all the complex maps here, the ones where the author really put in the effort are definitely "First Blood 2.4" and "podarok2001." Although, I passed them right away, practically without replaying any battles.
I also think the complex missions (campaigns by mahuta-phonex) are challenging.
Grigory's maps are interesting, but you can just run blindly into an attack and tear through everyone, without any strategic thinking about the map.
It would be nice to create a prize fund for inventing a very complex (passable) map, like $500 for the top 3 places. I would also try to create one.