The information from this article is up-to-date as of 22 September, 2020.
Iteration Selene is an NPC.
Selene's head has an elongated shape like a horse or a lizard, they frequently stick out their forked tongue indicating a reptilian heritage, specifically from a warm climate considering their clothing and the all around look of their head.
Facing the Nexus from where you park your ship, head to the left side of the Anomaly, and then go all the way to the back. There are several vendors here — Iteration: Selene is in the back left.
The metal tube next to them also offers frequent exosuit slot upgrades.
Exosuit upgrade tree
Once purchased, this can be used in the Appearance Modifier.