Gah, I thought I posted a reply to this days ago, but apparently the forum ate it. Let's try again...
Goblin-King: But I
don't want the Heroes to stick together. That's
their job.
I want them to get overconfident and/or paranoid, wander off alone like fools in a slasher movie and get dismembered by Wandering Gargoyles. Divide and conquer!

But you're right, I wouldn't want more than one or two affects-all-heroes cards in the deck per Quest.
Poison gas sounds like a good one. Might involve a little bookkeeping though (remembering whether or not the gas has dissipated).
Sjeng, I like the sound of a treasure trap that does
less damage than normal (i.e. you can roll to defend against it).
Ethica, that mighty spear trap sounds vicious. I'm a bit wary of such a powerful trap since they usually do automatic Body point damage - 2 might be too much. (Although I should look up those swinging blade traps from Ogre Horde, I seem to remember them being pretty nasty.)
Nerrad72, I can't open your file 'cos I'm still using Word 2003 - sorry! Could you put the text in a forum post?
Meanwhile, I've come up with the following cards of my own (flavour text now included):
Rats! - You hear a frenzied chittering in the walls and realise too late that your search has disturbed a nest of huge rats. They swarm out clawing and biting. Every player in the room is attacked with one combat die. The rats then vanish into the darkness. Return this card to the pile.
Bats! - A rustling overhead is your only warning before a storm of black wings descends upon you and your companions. The enraged carrion bats attack every player in the room with one combat die. The bats then flap away into the darkness. Return this card to the treasure pile.
Tentacles! - The noise of your search has disturbed something horrible lurking beneath the floor. Slimy tentacles burst into the room and attack every player present with two combat dice. After you have fought them off, the tentacles slither out of sight. Return this card to the Treasure pile.
Equipment! - A bundle of old rags and rat droppings turns out to contain a forgotten hoard of weapons and armour. Most are rusty and useless, but one is in good condition. Shuffle the Equipment cards and draw the top card. You may keep that item if you wish.
[Maybe too good? Equipment is usually in the Quest Notes, so maybe this isn't needed?]
Potion of Magical Resistance - The garish symbol on this bottle reveals it to be a Potion of Magical Resistance. You reflect sadly on the poor taste of wizards. If you are targeted by a spell, you may immediately drink this potion. The spell will not affect you. The card is then discarded.
[Imported from Wizards of Morcar but using the Barbarian Quest lightning-bolt-bottle art 'cos it's so amusingly tacky.]
Dead Body #1 - Huddled in a corner, you find the corpse of an unlucky adventurer. His body has been stripped of valuables, but by examining his wounds you learn how he died. Forewarned, you may ignore any Body point loss from the next trap you trigger. The card is then discarded.
Dead Body #2 - An unfortunate adventurer has met a cruel fate in this room. He carries nothing of value, but his wounds reveal that he was ambushed. Forewarned, you may attack the next Wandering Monster you encounter before it attacks you. The card is then discarded.
Nameless Horror - In a dank alcove you discover a small, gruesome effigy. Something about it makes your skin crawl. Even after you put it down, you cannot shake the feeling that it has glimpsed your darkest secrets. Lose 1 Mind Point. Do not return this to the pile, even though it is harmful.
[Meant to be rare.]
Hand of Chaos - You have triggered a sorcerous trap. A gigantic spectral hand plucks you from the room. The Evil Wizard player may place you on any unoccupied square that the players have already seen. Do not return this card to the Treasure pile (even though it is a trap).
[Inspired by those horrible hand things in Zelda games that dump you back at the dungeon entrance. Potentially the most annoying trap ever. Might be too easy to abuse...]