... I got nothing.
Oh, yeah, sources.
"Thrones has landed Icelandic art-pop sensation Sigur Rós to appear in season four. Jón Þór “Jónsi” Birgisson, Georg Hólm and Orri Páll Dýrason are currently shooting an appearance on the Thrones set in Croatia."

So, not on the wall then? Therefore it's safe to assume they're here for some sort of festivities? (you know what I'm talking about)
Thoughts, Odeck people?