I know that Xen has seen this picture before, but I thought I'd post it anyway.
These are Thracian warriors, but the figure in the front rank, who is armed with a two-handed
rhomphia, could equally be a Dacian with a two-handed
falx:-
As you can see, you cannot use a shield with such a large heavy two-handed weapon, so you had to be a bit of a nutter to use one....but then, the Dacians WERE a bit nutty!
You see, they believed that death on the battlefield would ensure entry into a sort of 'warriors heaven'. So, like Viking Berserkers and Celtic Gaisatai, they didn't bother with defensive armour, but usually fought partially naked to show how brave they were.
Therefore I agree with Xen: a figure naked from the waist up and armed with a large curved blade on a long two-handed wooden pole would be just about right.