These are just ideas but I think it would pretty cool if Tinyco used them. Click on the title link if you can't see the awful drawings.
Murky: Water & Shadow. A huge dark-skinned whale type creature. OR A Dark Newt
Black Ice?: Shadow & Ice. Not sure about the name but this could be lemming.
Coal: Shadow & Earth. A hedgehog.
Metal Hybrids:(TD98 came up with the metal element. Go to his ideas page to see it and other amazing drawings!) Machine:
Metal and Electric. A robot.
Gold: Metal and Light. A giraffe.
Rather than evolving into a Legacy Monster at Level 9, Legendary Monsters evolve into Gem Monsters. Rather than giving of coins though, these monsters would produce diamonds, albeit at a very slow rate. Certain combinations of Gem Monsters in their habitats would give off a greater diamond yield. Here are the Gem Monsters:
If you have any ideas what the missing ones could be, please leave a message.