Ian, if you want you can :
- found out the different capital cities for each province
- search about architecture of the different factions
- search about unit ideas for each faction (and change english names to celt/saxon names)

You can do some concepts art, and take a photo of those to put it on your PC ! Anyway, Lucterios (who works with me on Gallia : Total War) may do some concept arts later, when he have finished with those of Gallia TW.