I haven't really finished the Book I but I'm already dying for a book 2. Here's some of my ideas.
Game Engine
1) Keep the same engine. 800x600 is good enough and honestly the game looks pretty nice as is. Not that I am against 1024x768, I'd just rather you put those resources on the game itself so we can have more quests, towns, and dungeons.
2) Make Windowed mode resizeable. While i realize this might pixelate and distort the image, it's a nice option to have when you need to keep an eye on the desktop and keep playing. but 800x600 is TINY on 1900x1200 desktop.
Game Play
1) Balance out magic/character system. I've noticed a number of people seeing what I see, that certain weapons, spells, and stats aren't as balanced as they could be.
2) A "fast move" or run option.
3) A "Game+" mode. Basically after you beat the game you can play again with you your high level character but the mobs are harder and drop cooler loot.
4) New monsters, maybe with damage immunities. For example, swords do -20% on skeletons but bashing weaps do +20%. Also multi-tiled monsters like a dragon that's 6 tiles big.
Future Products
1) I like the idea of a throwback to games like EoB and Dungeon Master. But I think it should be a separate product.
2) I like idea of randomly generated dungeons, but I also think this should be a separate product.
Anyways that's my 27.95 on this topic.