Eh, the Celtic chariots were always of the light and deceptively simple-looking type AFAIK. Not that they wouldn't have been painted and so on of course, and probably have a few severed heads hanging here and there as a boast of the owner's martial prowess, but as their whole function was to be light and nimble "battle taxis" for the elite the Celts sure as heck weren't going to load them down with unnecessary bits and pieces.

And given how much they cost (given the actual technical complexity involved), the chariot itself was a status symbol enough even if left completely plain...

The basic charioteers look a bit bleh in their striped shirts and trousers though. Wonder if you could use something more macho like Milnaht or Rycalawre models instead ? The main snag I can foresee is possible trouble with the model refusing to present the spears as overhands/javelins, as I've seen happening when trying to convert the vanilla Pontic Heavy Cavalry into officers with overhands...