Playing through this really cool campaign I found on the workshop. It's called Berlin Blitz, and its set in WW2. Manny Pardo was set back in time to kill HItler, and there is a ton of custom stuff. There is custom cutscenes, assets, and sprites and weapons skins. It's a two level campaign, but I only completed the first one. It was pretty long, maybe 4 or 5 floors. Would highly recommend it. He even gave a download link for all the custom assets that he used, so that you can use them in your own levels.
Also found a level that was based on the 90s Doom. Just mostly been downloading a ton of campaigns and levels, Been really enjoying them, adds a lot to the game.