by Bloatoid
Death Wish https://www.moddb.com/mods/death-wish-for-blood If you're only trying one mod for Blood, this is the one. Features stunning and varied maps full of visual detail. All three episodes finish with some of the most epic boss levels ever made on the Blood engine.

by SpillSomeBlood
Eviction https://www.moddb.com/mods/eviction-addon-for-blood/downloads/eviction Each map has a different setting, forming a cohesive episode. Stunningly detailed with unique puzzles. A must-play.
Somewhere Under the Sea https://blood.freeminded.de/index.php?section=episodes&id=504 Bioshock-inspired levels. Challenging!
Return To Haunted Hill http://blood.freeminded.de/index.php?section=maps&id=544 Caleb clears out the Cabal infestation in his mansion.

by Tekedon
Castlevania 2 https://www.moddb.com/games/blood/addons/cvania2-blood
NES-inspired map with puzzles and great combat.
Not So Forgotten Catacombs https://www.moddb.com/games/blood/addons/not-so-forgotten-catacombs A A Blood Alpha-inspired map that will test your skills.
Count of Wallachia https://www.moddb.com/games/blood/addons/count-of-wallachia Take on Dracula himself in his castle.
The Slums https://www.moddb.com/games/blood/addons/the-slums The title describes the setting perfectly-excellent atmosphere.
GMNarnia polished https://blood.freeminded.de/index.php?section=maps&id=636 A map based on one of the Blood Alpha maps.
A Bloody Mess https://blood.freeminded.de/index.php?section=maps&id=600 Set in winter, similar to Episode Two.
Christmastown Massacre https://blood.freeminded.de/index.php?section=maps&id=613 Continues from A Bloody Mess.
Torture https://blood.freeminded.de/index.php?section=maps&id=581 Harkens back to castle and temple-style levels from the original game.
Sacreligious https://blood.freeminded.de/index.php?section=maps&id=568 Caleb takes on the Cabal in the desert-Sphinxes included!

by Skobbejak Games
Blood: Fleshed Out https://www.moddb.com/mods/blood-fleshed-out Best newcomer in years. Three episodes-though I suggest starting from Episode Two, which plays more like the original game. It employs jumping mechanics in spots that make map navigation a lot of fun. Top-notch combat and environments.

by Smooth Skin, WhirledTsar and Streaky
500 Milliliters of /vr/ https://www.moddb.com/mods/500-milliliters-of-vr/downloads/500-milliliters-of-vr A mix of maps from different authors. Unique settings you wouldn't expect in Blood-like a golf course, and a map set entirely inside a ventilation shaft.

by Damien_Azreal
Marrow https://www.moddb.com/mods/marrow/ Cultic-inspired episode released in 2023. Highly recommended!

by daMann, Damien_Azreal, BloodyTom and Matthan
Bloodbasket https://www.moddb.com/mods/bloodbasket Four maps that are top notch!

The high bar of the above entries is hard to beat, but these have the same greatness:

by Wangho, Red Fanatic
Bloody Pulp Fiction https://www.moddb.com/mods/bloody-pulp-fiction-bloodgdx-ready/downloads/bloody-pulp-fiction-bloodgdx-ready A multi-episode mod with some great highs. Episode One kicks things off with especially strong atmosphere and satisfying combat-it really sticks with you.

by Tedd
French Meat https://www.moddb.com/mods/french-meat-2/downloads/french-meat-v23 Packed with atmospheric and fresh settings, plus intense combat. Episode One is a must-play!

by Bloatoid
Hostile Takeover https://www.moddb.com/games/blood/addons/hostile-takeover-v11 Earlier work of Bloatoid.
Inherit The Earth https://www.moddb.com/games/blood/addons/inherit-the-earth Another earlier work of Bloatoid.

by Tobey (Tobias Persson)
Fresh Blood ("Fresh 1") https://blood.freeminded.de/index.php?section=maps&id=51 Mansion/haunted house setting with amazing gameplay!
Meat Factory ("Factory") https://blood.freeminded.de/index.php?section=maps&id=277 Industrial-style level.

by James Wilson III et al.
The Lost Episode https://www.moddb.com/games/blood/addons/the-lost-episode An episode built from unused maps from the Blood alphas. The non-linear level design feels authentic-no surprise, since it’s based on work from the original developers.

by VictoriousGames
Blood - Extra Crispy https://www.moddb.com/mods/blood-extra-crispy If you want to change up the game, this is your mod. It overhauls weapons, enemy behavior, and more. A well-balanced mod-and whenever I play with it, it's a ton of fun. Exclusive to Fresh Supply.

Many say source ports are the best way to enjoy Blood instead of launching Blood: Fresh Supply directly from Steam. These community-made ports offer better customization and compatibility, but aren’t required to enjoy the game. If you want to try them, I highly recommend BuildLauncher https://www.moddb.com/news/buildlauncher-a-frontend-for-build-engine-games a great frontend that lets you try out different source ports and download many of the mods listed here from an easy interface. Raze is a good starting point if you prefer a movement feel similar to Fresh Supply. BuildGDX offers more customization.