An accurate 54mm celtic figure is very hard to find. It should not have
- fur clothing
- pig tails, long beard
- more than 2 weapons
- a plume or panache on the helmet
- bracelets
- axes (there are exceptions - what I mean are "standard axes")
- horned helmets
Of course there are "rules" within the centuries and definetly each piece of the equipment must harmonize in time and area. It nothing else like, let me say, an english soldier. You can't make one with a steel helmet M1917, a brown bess, a cross bow and a mediveal breast plate.
To be honest, I don't have one myself, except two bare breasted examples from Andrea and two 120mm samples which where sculpted but never get into large scale production.
There are some chances to convert early Latene-celts by using Greeks with Linothorax and giving them celtic helmets, swords and shields and late Latene celts by giving roman soldiers celtic shields, trousers, long swords and very early Weisenau/gallic helmets. Middle Latene celts can be converted also, as there are some examples with correct helmets (remove any plumes or panaches), using chain belts and correct swords.
Pegaso Celts are completely fancyful, Romeos are not quite better and Andrea's could be the basis for a conversion.
Or: Take one which fits your taste and have fun with painting it. That's what it should be.
H