This is an idea I had a little while back, but forgot to make a thread for it.
I think there should be a very subtle particle effect on corpses that have not yet been looted. Guild Wars 2 does something similar to this, where dead enemies have a slight golden sparkle to them when they have unclaimed loot. It wouldn't be anything drastic, probably just similar to the green effect that blighted resources give off. It would make it easier when killing large groups of enemies, since I know I've had times where I attempted to loot the same enemy several times because I forgot if I did or not.
I have other suggestions when it comes to loot itself, such as making it instanced to individual players like all quest drops are (especially for players in groups), but I'll just leave my suggestion to this for now. c: