There seem to be enough bodies of water in Skyrim that it would be feasible to have blood not fade after combat, but only wash away if it rained or you took a swim. Not only could we follow a stream out of some dungeons but we could use it to wash off. What do you think?
Meh.
Sounds kind of silly, honestly. (Also, quite ugly - I was glad I could turn off the Massive Blood Spray in Dragon Age 1, just because it made everyone look ugly, and stupid, in post-battle cutscenes).
But, hey - personal preference.
(I'd guess that blood splatter fades just to keep processing overhead down - if it kept building up more and more decals as you hack your way through a "dry" dungeon, it could probably start to slow things down on lower-mid systems. Especially if you had several quest NPCs with you also getting splattered.)