. . . wonder what their capital will be - Lutetia, Pyrene, Noricum, Numantia?
There are some reconstructed/preserved Celtic city name available, but with less glamour.
Thanks for not giving them druids as EU!
There are actually quite a few Gallic City Names available, since the Romans 'Latinized' a bunch of them and re-used them or Roman /Greek writers recorded the originals:
Bibrax or Bibracte - the largest, may have had a population of over 20,000, which would make it as large as Medieval Paris
Samaurobriva
Noviodunum
Durocortorum
Mediodunum
Tolosa
Arelate
Massilia
Condatum
I compiled a list of over 20 some time ago when I got tired of playing the 'Celtic Blob' in Civ V.
If I recall correctly, a lot of the inspiration for the "Celts" is based on the Gauls, similar to how the "Persians" are based on the Achaemenid (did I spell that right?) dynasty. I would have to double-check that with our historian, though.
Gauls would almost have to be the primary influence, since they were just about the only Classical Era Celts that had reached the City-Building stage
There are 'Duns' or Oppidums/Oppiduns all over central Europe down to the Balkans and throughout the British Isles, but no population concentrations like cities except in the Celtic lands west of the Rhine and north of the Pyranees - Gallia.
And, of course, the
Gaesetae or 'Gaisatai' were, according to Polybius, a 'Warrior Order of notable courage and ferocity' of a single Gallic Tribe, so specific to the Gauls - although naked warriors carrying long iron swords were common to most of the Celtic groups, as Celtic nobles in link mail with stout wooden shields and swords were also common and Latin even had a specific word for a Celtic javelin/throwing spear: 'gaes' so one has to assume that it was a common Celtic weapon as well.
"Nemeton", on the other hand (or words related to it) or 'Sacred/Druidic Groves' were found Everywhere, which probably reflects the cultural solidity of the Celtic World as opposed to any political unity, which was non-existent
. . . The Gauls were a sophisticated, educated, urbanized culture. Their metallurgy was some of the finest in Europe, and there was a high demand for Gaulish craftsmanship in Southern Europe, which they traded for Mediterranean wine and other luxuries.
Among the things invented/developed by the Celts:
Link mail ('chain mail') armor
the long iron sword
Soap from animal fats while the Mediterranean World was using Olive Oil
the wooden barrel - from either Gaul or Germany, no one is entirely sure which, but a revolution in shipping equivalent to the Standard Container of the 1950s CE.
Iron plows - not as efficient as the Medieval wheeled plow, but sufficient to plow the heavier soils of northern France
Pattern-welding for swords
well-surveyed, well-built roads - at the same time the Romans were building theirs, with distances surveyed so accurately the Romans kept using the same surveys centuries after they had conquered Gaul!
So, In-Game Celts should at least be well-armed, well-traveled, well-fed, and Clean!