In the Guardian of the First One boss, the room is covered in sand. The Bronze Shrine in Dragonblight is also covered in Sand, as is Tanaris where the Caverns of Time are.
This is a pretty big jump, but there are several other hints that have people theorizing the First Ones (and the "seventh aspect") are Time. The statuette artifact in Korthia has whispers that reflect the idea of Time and there are several hints of an "infinity" theme going on with Oribos, Bastion (see: the skybox with a big golden infinity logo) and now the Arbiter/Jailer's sigil. As we know, the Infinite Dragonflight is all about time.
What are the odds that the First Ones are only first because they time traveled back the beginning?