Having loot proportional to the size of the room would be excellent. As it is, I tend to ignore large rooms altogether due to the effort required to get a rather small amount of reward.
Ed: On that note, it might be interesting to supply throw-away loot the same way trash enemies tend to, to avoid oversaturation of valuables. Maybe small mana / health regeneration instant-use items based on the level of an area. You walk over it and get 10-20 mana back, for instance, sort of encouraging exploration further without dumping a truck of treasure on the player?