Nice mod, makes me to remember the original game. Like else have sed the corridors are too narrow, rooms are too small and battles are just slashing and theyre quite hard.
So here are few ideas :
MANUAL (I didn't understand much of this althou I've played the original boardgame. Comprehensive info on quests, eqiupment, game play etc...)
More character classes (all or just dwarf, so you don't need to do magic)
Larger rooms & corridors (its way too dense now)
Altering the battle (its just slashing and running now)
More quests (see below)
More equipment and maybe some spells.
Once you cleared the room no more enemies would spawn in there.
MAP (placed on the wall?)
Perhaps a chance to find stuff in every room, like in the boardgame, through random chance.
If you want to stay true to the original game you might want to change the travelling system, so world map would not be needed. Instead player would be teleported to another dungeon & gathering point
If youre short on ideas read the original game manual!
Heres the US Quest book in pdf
http://www.hasbro.com/common/instruct/HeroQuest,questbook.PDF
and heres the manual
http://www.hasbro.com/common/instruct/HeroQuest.PDF
Heres quest book in pdf for H&Q expansion pack Kellar's Keep
http://www.hasbro.com/common/instruct/HeroQuestKellarsKeepQuestBook.pdf
Another addon Return of the Witch Lord
http://www.hasbro.com/common/instruct/HeroQiest-ReturnoftheWitchLordQuestBook.PDF
The Frozen Horror
http://www.hasbro.com/common/instruct/HeroQuest-BarbarianQuestBook,thefrozenhorror.PDF
The Mage of the Mirror
http://www.hasbro.com/common/instruct/HeroQuest-QuestbookfortheElf,themagicofthemirror.PDF
Read those and you surely won't run out of ideas!