I would do a wall of pictures of things that you all have in common. For example, pictures of your city, local attractions (monuments, museums, a park, trees in autumn, winter, spring and summer..local beach, etc. Get a tourist map of city (from local tourist office...these are usually really colourful and have points of interest on them...photograph points of interest). Maybe a before and after photo of your lobby! Lol
I would do the entire wall. Make sure you secure them to the wall or you will be forever straightening them up..or picking up broken pieces of the floor. Restaurants pre-drill with a "countersink" drill bit..and screw then to the wall. You can also put them up as you normally would...and then put Velcro to secure them in place.
I would paint the gallery wall a dark grey, the ceiling white, and the other wall the lightest shade of grey from the sample stub and then with painters tape and a level...make a nice striped wall using water based varnish to paint them on (just varnish, in a higher sheen than the paint on the wall). This application will give your wall a very light shaded look that won't look busy.
Ceiling light, track lighting to make the room brighter and highlight the wall hangings.