This is a great image.
The only thing two things I see are:
1) The three workers are the focus of the image. The middle one is the best in focus. Because of the narrow depth of field and the workers not all being the same distance from the camera the outside two do have a softer focus. For an art piece this isn't really a bad thing but it may be something to watch for in the future.
A couple of ways to solve this is to close down the aperture (I wouldn't. Shallow depth of field works here) until the three are in focus or put them all at the same distance from the camera.
2) there is some aromatic aberration in the image. Look at the back of the jacket of the middle worker and you will see some green fringing. This is likely a product of the lens you are using. Depending on the post processing software you are using you may be able to remove/minimize this.
Again this is a great image and most people will never notice what I put above.