My apologies for bumping this thread on such short notice, but it'd be foolish to let it go to waste.
With that said, I'd recommend the following mods:
Lunar Shadow (Interesting lore/great for those looking for a Castlevania styled experience. It's mostly complete, though it still has some unfinished content. If it's too easy for you, Selenic Shadow is similar but more challenging)
Hope of Shane: FROST (Unfinished, notable for having a long intro cutscene which can be skipped. Was one of 4 versions of Hope of Shane that was sadly never finished)
Battle Spire Challenge (A unique take on the Boss Rush mod formula which pits the player against several boss combinations. There's also a hidden weapon which comes with some interesting lore)
Enthology- The Lost Chapters (A mod which changes things up in every chapter, the game saves automatically and has developer commentary)