Sepia

Sepia is a 34-map megawad (which started as a NaNoWadMo project) with maps ranging from lighter brown shade to darker brown shade. The mapset is mainly targeting DSDA-Doom (Woof should also handle it, but it wasn't tested), but GZDoom should work for the most part as well (use it at your own risk still, there might be more issues than i found). The mapset is divided into 4 episodes with themes variying from the trench warfare of the WW1 to abstract solid-colored places in the void. Difficulty varies as well, with the wad starting fairly tame, but getting progressively harder both in movement department (episode 3 being heavy on the plaftoming side) and in combat department (episode 4 being heavy on the slaughter side).