Although I have used 15mm scale for my SSD playtesting, the rules, as with all Ganesha Games, work at all imaginable scales. 15mm and 28mm scales arguably have the most choice in terms of civilians, but I have just had my attention drawn to these fantastic looking 1/72 scale ancient civilians by produced by Strelets.
There are a number of packs that would prove really useful for an ancient setting for Song of Shadows and Dust. I can only showcase one pack, the so-called 'Ancient Christians' who have been previously shown off over at Paul's Bods. I have to stress that the images of the figures themselves were painted by the obviously splendid example of all things wargamey in Germany, Paul.
I think you'll agree, Paul did a marvelous job with these - his blog also includes witty comments accompanying each of the images. These are a far cry from the 1:72 scale plastic Napoleonic stuff that I owned back in the early 90s. They are actually very nice sculpts in their own right and could hold their own against a well painted metal figure. It is also pretty obvious, that although the pack is called 'Ancient Christians', they would certainly serve as ruffians of all faiths and backgrounds.
Strelets also appear to do three different 'Spartacus' packss, of which the photos of the figures below come from the second uprising pack.
And several other more generic packs which might make a wonderful contribution to an ancient city-scape. From what I can tell, each box has about two dozen figures and retails in the UK for a little over a fiver. What more do you need?