So you're just gonna come in here and spit straight good ideas?If you break down the most iconic ones you have: flying enemies that inflict poison, wall crawling enemies, and tortoises. Then you can split these across three jungle alter egos: sinister swamp, bloody bog, and rainbow rainforest. I once made a few ideas (that I really love sharing).
Hornet variants: Plague Crows (slow, powerful feather projectiles that inflict poison), Malaria Mosquitos (shoots very weak, poisonous, ichor-like streams of red blood that are hard to dodge), Starfruit Bats (spits average damage poisonous seeds like a machine gun).
Jungle Creeper variants: Corrupt Centipedes (worm-AI, can climb along walls, drop rotten chunks), Bonerantulas (basically an upgraded Creeper, also a Zelda reference, drop vertebrae), Glowtail Geckos (positions itself in range and launches confusion inflicting tails).
Tortoise variants: Cursed Snappers (start slow but get more vicious as they approach death, inflict and drop cursed flames), Ichor Boneplates (can periodically crumble into a pile of bones as a defensive technique, inflict and drop Ichor), Crystal Softshells (release close range fragments of crystal mid-flight, inflicts bleeding and drops crystal shards.
I mean, yeah, all they really need to do is make different grass types able to grow on mud, but this would be so awesome!
Also, maybe there'd be plantera variants. Not in their name or drops, but their sprites and perhaps their music.