I’m not a very good builder or modeller, but I had a crack on making a self check-in machine for an airline. It looks OK but I don’t know how to make the back of it look better. It looks really bland to me right now.
Perhaps something that you could add on the back is a screwed in cover that people would use for maintenance on the machine. It could make it look more realistic.
Don’t make the screen take up the entire surface, it’s too large. As for the back, use either a plugin called ro-peater to make a higher quality curve. Remember to union everything, add more buttons, screws to the base of the model and maybe wires at the back.