Expanding on my ideas:
Water/Grass-Two stage. First is small amount of Seaweed it's in a humanoid shape(A small child), it then evolves into a large batch of Seaweed also humanoid but more monster-like.
Electric/Ice-Two stage. Arctic Hare. First stage is just a typical Arctic Hare with some Yellow mixed into it and some other little touches. It then evolves into a bigger version with thunderbolts on it's legs and back.
Grass/Rock-Three stage(Or two would be fine). First is of a rock with a little Moss on it, as it evolves the Moss grows, it's final evolution would have the moss completely taking over the Rock.
Ice/Grass-Two stage. Some Grass that has a little frost on it. Final evolution would be a lot more frost.
Fighting/Rock-Standalone would be fine. Not sure if there is anything out there that would work alone with the type, if not then just a humanoid with a rock belt and some other rock features.
Poison/Flying-Two Stage. Flying Snake. Starts out Poison, a baby Snake. Then it evolves and gets it's wings...well not literally, although if they want to do that instead I'd be fine with that.
Bug/Ground-Standalone or two stage. Earthworm. Pretty much just an Earthworm, maybe some soil worked into it's design.
Flying/Steel-Two stage. An Airplane that evolves into a Rocket.
Psychic/Rock-Meteorite is all I can think of, so I guess an evolution to Solrock and Lunatone.
Bug/Water-Three stage. Rollie pollie
ollie(Woodlouse, has many names used for it). Start out as a typical Woodlouse, it evolves into a sphere version of it. It's final evolution would have it's backside rolled up but it's front will be open, would be a little long.
Rock/Dark-Standalone. Gargoyle. I suppose Druddigon is kind of like one, but whatever, I'm sure they can make it different enough.
Ghost/Bug-Two stage. Ghost Spider. Starts out as Bug/Poison baby Spider, then it evolves into a more ghostly Spider(Taking it's name more literally), it loses Poison for Ghost(It can probably have Poison Touch/Point as an Ability).
Dragon/Fire-Two stage. Just a generic Dragon. Maybe there can be branched evolutions for it, so it starts out pure Dragon then either gains Fire, Water, or Grass.
Dark/Fighting-Standalone or two stage. Humanoid thing that is focused on some kind of fighting style but it uses dirty tricks. If it's two stages then maybe it can be pure Fighting that turns to dirty tricks upon evolving.
Steel/Water-Standalone or two stage. Put a Fish into some armor or something. Really, just take any Fish or Marine Mammal and slap some armor onto it. Shark, Whale, Dolphin, Swordfish(The Steel can be more for it's sword-like bill thing), etc...