Playing Celts

[Watchman]

That's weird, it worked just fine when I tried it.

Checklist:
1 - delete map.rwm from \Rome - Total War\bi\data\world\maps\base
2 - cut-paste the factions you want under "playable" in descr_strat text in \Rome - Total War\bi\data\world\maps\campaign\barbarian_invasion; I'd leave
romano_british
ostrogoths
slavs
empire_east_rebels
empire_west_rebels
slave
under "unplayable" if I were you.

That worked for me, anyway. The Celts, Berbers et all were neatly in the faction selection screen and a short practical test proved the Berbers worked just fine in-game.