Basic idea: Drops should be more monster-dependent.

This doesn't mean that monsters should always drop a certain kind of item, but instead a skewing of probabilities towards certain items. For example:

• Mages/priests would tend to carry spell books more often
• Archers would tend to carry quivers of arrows
• Mushrooms would obviously always drop shrooms

This adds an extra layer of strategy: you know that if you need a spellbook, you kill mages, or if you want arrows, you kill archers. This puts item distribution under the player's control a little.