I'm basing them on half-size bases, 20x10mm instead of standard Warmaster 40x20mm. Why? Well, there are a few reasons:
1. Warmaster Ancients has great fast rules that allow for huge battles. But with default unit sizes those units are so big they require a table of insane proportions to stage such a battle. Halving the bases and all ranges allow to have a big battle on relatively small table.
2. Money and painting. If you halve the bases and buy 1000p army, you get 4000p and obviously painting is also 4 times as fast.
Below some pics of Romans and Britons I have painted so far. I tend to paint 3 units (18 stands of 6mm infantry) in a go, using the Army Painter dips.
They can also be seen here:
Google's gallery allows for some magnifying.