In honor of Doom's 30th birthday, a team of Doom modders led by Joshua "Dragonfly" O'Sullivan just released a sequel to six-episode Doom megawad Eviternity. Eviternity two likewise has six chapters, each made up of five maps with one secret map per chapter. That's a grand total of 36 maps you can download right now.
Eviternity 2 uses a newly updated version of the OTEX texture pack, which means it'll look sweet whether you play it in DSDA Doom or GZDoom. I've had a look at the first couple of maps, and there's some nice use of colored lights and rain already.
It's best to play through the original Eviternity first, since this is a sequel in terms of its difficulty as well as its story. In fact it begins by sending you backward through the final levels of Eviternity, which is a nice celebration of your victory. Looking back, Eviternity has some amusing similarities with Doom Eternal, being a quest through transcendent, heavenly locations to confront an angelic being. Though given that Doom Eternal was already in development when Eviternity released they're presumably coincidental, of course. Following the defeat of Hell with a war in Heaven is just the obvious cool thing to do.
If you want to play Eviternity 2, it's designed to be played with the Doom 2 IWAD and you'll need to make sure your copy of DSDA Doom or GZDoom is up to date. You can grab either from the same website as Eviternity 2.