Thanks, Kam - you are presenting us with an ambitious multi-figure composition, employing a background sourced from the impressive HBO set for 'Rome'. A dozen human figures with appropriate shadows, the dog and at least two wooden signs, earthenware vessels, and three sets of chains and manacles have been inserted into the original scene. This represents a lot of work which is not immediately apparent.
Your current avatar is now identical with that on DA, and it reappears discretely as a signature below the Latin inscription on the overhead sign. The lettering is neatly applied, I think advertising the 'best choice of virgins from all over the empire' - evidently an honest slave dealer's establishment, judging by the attractive girls on display. They have been secured by chains in positions which keep them out of the shelter of the awnings, but where conversation may be possible between them. But from what you tell us of their origins, they will find it hard to identify a common language.
I think the sign has been created as a proper rectangle, the lettering applied, and the whole thing distorted to an oblique, elevated angle? The Greek sign seems to be similarly produced and compressed, according to perspective requirements. It seems to imply trading by an educated merchant, or a Greek tradesman, as you suggest.
Not for the first time, we see your delightful device of interaction between the kneeling girl and the dog - providing a neat contrast between their stations in life. I recognise the group of three figures conversing in the distance, supplied together with the character modelling purple headgear, via another HBO scene which is proving popular with manipulation artists. The soldier and his attendant derive from a further HBO source, indicating how useful this series is to manipulators of ancient Roman scenes. These two appear to be looking directly into the faces of the slave girls, in a manner which is very credible. I do not recognise the slave dealer himself - perhaps he is also from HBO?
The four girls are indisputably the leading ladies of your picture, and the merchant's claim is endorsed by the ethnic variety, which is nice to see in a Roman illustration. The lightweight chains and shackles provide adequate restraints for the girls. Whilst subtly applied, these features embody close attention to detail and they are rather neat.
As the background is an empty street with a low viewpoint and forced perspective, the only clues for figure scaling are the receding doorways. I think this has been a challenging scene to populate, but you have brought it to life very effectively as a snapshot from ancient times. Well done, Kam!