http://cloud.steampowered.com/ugc/648748815422290244/D70453BA8B233CAADB91DAE0501B7D36EE6BD107/

http://cloud.steampowered.com/ugc/648748815425012323/E9EB73EFC3F6E5E20FBB06F7FFF172DC12E7DFEB/

http://cloud.steampowered.com/ugc/648748815422293956/19B02F06F102AF86CD2F56F0998E192EB7AD3167/

So what culture do these markings belong to if any? Any clues?

Nordic? The designs feel somewhat Nordic. But I have not noticed these on any Nordic tombstones throughout the game.
Dunmer?
Orsimer?
Nothing just arbitrary decorations of no real importance?

I'd go with Falmer, simply because I can't think of anybody else...

That, I'd guess.
I'd think they were created with "nordic culture" in mind (and I do think I've seen them on some graves in locations built by Nords), but were used as just a general gravestone texture without thought to the appropriateness of the designs in that specific context.

I've seen them on tombstones in the Falkreath graveyard. They're too similar to Nordic Ruins to be anything else. Just very ancient, very Nordic, possibly dragon worshiper origins.

From the look of them, I'd warrant a guess that they're proto-Nordic ceremonial burial markings; especially since these are found on those proto-Nordic burial urns too - if memory serves correct.

Maybe the Nords copied some of their markings from the Falmer.

They're ancient Nordic. Also found in barrows, on various nordic clutter, and on giants. The reason they appear on Orcish and Dunmer burials is because Beth only made that one gravestone texture.

It's a sort of anti-giant perceptive trap, like the nords place on certain cows. Giants, big lumbering beasts that they are, have a compulsion to plot out their whole course ahead of time. When standing atop a mountain, looking down at the hills and valleys below, a giant will spend hours meticulously plotting the path he and his heard will take as they make their great migration. Wide, gentle swirling patterns trick a primal part of the giant's mind into thinking that he's looking down on distant valleys, putting him in a quasi-hypnotic state. While the giant is thus enthralled, nords can get away with the rest of their herd, or even dig up & relocate the bones of their ancestors. The giants actually enjoy this form of hypnotism, and so the practitioner of swirl-warding has nothing to fear in the way of Gigantic revenge, so long as he does not use it excessively, or to harass the giants. Dunmer and Orsimer living in Skyrim have learned to adopt this practice for simple reasons of self-preservation.

This is what I thought lol
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