I never had a problem missing things due to the graphics. Switch the darkness setting in the graphics options to 50 to increase the size of the light radius around your character, and bump the gamma up a bit to lighten the screen in dark areas (though you don't want it too bright above ground).
You can hit the Alt key in DD to highlight doors and loot, etc, though this will also set the inventory/stats of nearby chests/NPCs/equipment.
