Xerath's dance is known as "industrial dancing", which is evident in the song Pong by Eisenfunk. A comparison can be seen here.
There's an interesting mechanic that can be seen with his Classic, Battlecast, and Runeborn skins. When an enemy is hit with Arcanopulse, they leave behind a purple ball, revealing them. The Scorched Earth skin does not seem to have this.
From the lore, many people believed that Xerath was going to be Alowicious Chucat, a master artificer who died working on the Šablóna:Ii. This was disproved with the release of Xerath's backstory.
In his classic skin Xerath is shown breaking from a cage and destroying several chains , this is the sarcophagus mentioned on his lore and is the moment in which he escaped from it.
In Xerath's champion spotlight, Battlecast Xerath was called "Lockdown Xerath" and Runeborn Xerath was called "Runeforge Xerath".
Due to the community's popular demand, both of Xerath's skins were reworked. They both received new particle effects and colors due to them being too similar to the Classic skin before the rework. Battlecast Xerath has red particles and Runeborn Xerath has green particles.
Scorched Earth Xerath might be a reference to the military doctrine of Scorched Earth, in which anything deemed useful to the enemy is destroyed.
Scorched Earth Xerath's appearence and armor bears a similarity to Pyroviles, a volcanic alien species featuring in the fourth series of Doctor Who - "The Fires of Pompeii" episode.The Skin's splash art features a volcano in the backround that shares a resemblence to Vesuvius.
If Mordekaiser's ultimate, Children of the Grave, is on Xerath when he dies, the neon coloration of the skin will still be on the ghost. Classic skin will be blue, Battlecast will be red, Runeborn will be green, and Scorched Earth will have a lava texture.