To those who propose a desert / quicksand setting... If you get stuck in quicksand, what happens?
...if you get stuck and lose your turn (on some die roll) then it's essentially ice.
...if it slows you down (2 mp to cross) then it's essentially mud.
...if you get stuck (and presumably then roll a strength check to get out) then it's essentially web.
All these effects already exist. What's new? That's key, that a new type of tile has to add something fundamentally different.
Some ideas come to mind:
Copper Treasure: Iron Boots (Other) - immune to effects that move a hero. (includes Knockback, Poltergeist, Telekinesis). May be too much like the unmoveable skill.
Copper Treasure: Magic Eye. Heroes can set this down, and retain vision (block spawns) with it. If they leave it in a dungeon, too bad they leave it. So they'd have to go back and pick it up, else just give it up.
Town Item: Grappling Hook - Performs like a ranged weapon, but for 2 Surges, you may grapple and pull any small (1 square non-leader / LT) monster to you. Of course change Ghost to be immune to Grapple.
Potion: The Morph potion idea was really cool, I like that one.
Doors - How about a steel bar door, (like a prison gate) instead of solid wood doors? Magic and Range attacks could pass thru them.
Monsters:
Tier 3 (since each set comes with at least one tier 3)... Hydra (gets 4 attacks?)
Tier 1 - Green Slime? (Eldritch) comes in bits of 2-square and 3-square plastic "L" parts that fit together like Tetris pieces, but can move around freely so long as they're connected. One blob of slime could be composed of 10 of these, which can extend themselves out in any funky way. Attacks by Melee, doing very little damage, but ignoring armor. Like 1 blue die on the attack, ignoring armor. This one answers that call for an Eldritch that attacks via Melee, but still is sufficiently Eldritchy.
Melee - Dont think we need more melee. Already Ogres, Trolls and Giants are too similar. Perhaps something mid-tier, like a 2-spacer. A Centaur? This makes for a nice Ranged Melee character.
Eldritch - Some sort of Conjurer / Summoner? Someone who can bring about new monsters via a non-spawn method. Could also call upon acid rain, clouds that block vision, or thundering sounds that use a new template, a round template that's 7 squares in diameter, and rounded. He just points to a square, and the effect centers on there. (in other words, every square within 3 spaces of the target square, following flat edges). This would allow them to include a new template.
Just some ideas...
-mike