Foxes are a symbol of cunning, wisdom, and passion.
In the theme song, the Fox Miraculous briefly appears in the Miraculous jewelry box, although it is obscured by the raised middle section of the chest box with the Ladybug Miraculous and Cat Miraculous.
In "Volpina", Lila purchases a necklace with a similar design to support her lie to Adrien that she is a Miraculous holder, and it becomes her akumatized object.
Thomas Astruc reaffirmed that the necklace is from a store on Twitter, acknowledging that the scene where she gets it is very short and easily hard to miss.
In the Miraculous spellbook, one of the codes on the Fox Miraculous page translates to Volpina, but it's unknown if it's the name of the Fox Miraculous holder depicted or an Easter egg.
When Lila is akumatized, becoming a copy of Volpina, she gains the power of illusion, but it's unknown if this is the real Fox Miraculous' power.
At the Anime Expo 2016 panel for the show, it was stated that the wielder of the Fox Miraculous (not an akumatized villian based off of them) "will be potentially a recurring character."
This was confirmed again at the panel at San Diego Comic-Con 2016, along with that the Fox Miraculous and its wielder will appear in Season 2.