I am in the process of re-arranging the small display walls that I have in a tiny "library" adjacent to the family room. I am awaiting two prints on Metal from Bay Photo. Then the "fun" of taking down current images and putting up the new arrangements. I'll post a photo when done. In the meantime, let me address some of your questions.
I print on either paper or metal. The scene determines the choice. Scenes with water, reflective surfaces, etc I usually put on metal. When printing on paper, I always use a mat and framing. Also, when printed on paper, the mat will provide a space above the print so that the print is not touching the archival glass. Archival glass is important to minimize fading due to sunlight, artificial light, etc.
I like a thin black metal frame around the images. However, some of my pieces are also framed in black wood.
I always try to display the prints out of direct sunlight.
In addition to walls, I have a couple of images "featured" above our entertainment center in the Family Room. These are sitting on large easels.
When we moved in to this home, I needed a "quick" wall arrangement above a sofa in the sunroom. We had just been to India....so...I now have an arrangement of images from India in our sun room....
Note: The books on the round table are also mine....
To determine a nice arrangement and spacing, I lay the pieces out on the floor first.