Dark Sun monsters I haven't seen converted yet:
Original box
Animal, domestic: Erdlu, Kank, Mekillot and Inix
Belgoi
Dragon of Tyr (though that's more of a specific NPC, so we'll let that slide)
Dune Freak
Gaj
Giant, Athasian
Gith
Jozhal
Silk Wyrm
Tembo
Dark Sun Monstrous Compendium Appendix I
Animal, Household: Hurrum, Critic, Renk, Ock'n
Animal, Herd: Kip, Z'tal, Jankz
Antloid, desert: Dynamis, Soldier, Queen, Worker
B'rohg
Banshee, Dwarven
Beetle, Agony
Bog Wader
Brambleweed (and -tree)
Burnflower
Cat, Psionic: Tagster and Tigone
Chn'thrang
Cistern Fiend
Drake, Athasian: Air, Earth, Fire, Water
Dune Runner
Dune Trapper
Elemental, Athasian: (Lesser|Greater) Air, Earth, Fire, Water (though that's somewhat mollified by elementals now coming in Small, Medium, Large, Huge, Greater and Elder - not precisely like these ones though)
Erdland
Esperweed
Flailer
Floater
Giant, Athasian: Island, Plains, Beasthead
Golems, Athasian: Ash, Chitin, Obsidian, Rock, Sand, Wood
Halfling, Renegade
Hej-kin
Id fiend
Insect swarm, Athasian: Mini-kank
Kank, wild
Kirre
Megapede
Mul, wild
Plant, Carnivorous: Blossomkiller, Dew fronds, Poisonweed, Strangling vines
Pterran
Pterrax
Pulp bee
Pyreen
Rasclinn
Razorwing
Roc, Athasian
Sand Bride
Sand Cactus
Sand Vortex
Scrab
Silt runner
Sink Worm
Sloth, Athasian
Spider Cactus
Spider, Crystal
T'Chowb
Thrax
Tohr-kreen (later changed to Zik-trin'tal)
Villichi
Zhackal
Zombie Plant
Dark Sun Monstrous Compendium Appendix II
Aarakocra, Athasian
Animal, domestic: Aprig, Carru, Mulworm, Sygra
Aviarag
Baazrag
Baazrag, Boneclaw
Bloodgrass
Cactus, Hunting
Cactus, rock
Crodlu
Dagorran
Dhaot
Drake, Lesser: Magma, Rain, Silt, Sun
Dray
Drik: Regular and High
Dune Reaper: Drone, Warrior
Dwarf, Athasian
Elemental Beast: Air, Earth, Fire, Water
Elf, Athasian
Fael
Feylaar
Fordorran
Giant, Shadow
Golem: Magma, Salt
Gorak
Halfling, Athasian
Jhakar
Kaisharga
Kes'trekel
Klar
Krag
Kragling
Lirr
Mastyrial
Meorty
Mul
Nikaal
Pakubrazi
Paraelemental Beast: Magma, Rain, Silt, Sun
Psionocus
Raaig
Racked Spirit
Retreiver, Obsidian
Ruktoi
Ruvoka: Brajeti, Ethilum, Kaltori, Zathosi
Sand howler
Scorpion: Barbed, Gold
Seed, Brain
Silt Spawn
Slig
Spider: Dark, Mountain, Silt
Spinewyrm
Ssurran
Stalking Horror
Tarek
Tari: Tari, Warrior, Chieftain
Trin
Tul'k
T'liz
Wraith, Athasian
Xerichou
Zombie, Thinking
And then there are a bunch in various supplements as well. And that's just for Dark Sun - other settings probably have similar numbers of monsters waiting for conversion.