Hi Mark Many thanks for your well thought out comments on this image. I appreciate your dilema with regards to the lens length used and I think a longer lens, as you say, would provide a different shot all together. Here, I wanted to create a sense of space within a very small space.
Honestly, I have no constructive critique or ways to improve on this image. It is very excellent in so many ways. The friendship and good humor shown in the image is warm and wonderful and this image reveals a pleasant and warmly human setting.
While I can not tell you what would improve this image, I might be able to suggest a different sort of image that could be taken here. Perhaps an alternate view taken at a longer focal length, in the 30mm DSLR range. The short focal length used here does a great job of showing the shop and placing the people in a context. In an additional photograph, perhaps a longer focal length would take us closer to the people, showing some of the intimacy involved in cutting hair and giving us a more intimate view of their faces and friendly expressions.
The shorter focal length makes the space appear large and open, which perhaps it is not... Most such shops are often cluttered and close, and pleasantly so. The challenge, of course, is to find a camera perspective that shows the intimacy of this scene while still showing enough of the room to give the viewer a sense of place.
But after writing this, I must say that I'm not at all sure that my words are at all helpful. You have taken a masterful shot here as it is, and I doubt that I could take a better (or equal) shot! Bravo!!