Above the sofa is a great place to put your newly acquired pictures. Most people hang their photos too high. Remember you want to be able to see the photos comfortably. This means the center of your photo should be at eye level.
Scale is something else to consider. According to Art.com directer of merchandising, Linda Crisolo, art work above the sofa should be at least two-thirds the size of the sofa. What this means is if your sofa is nine feet long your art work should take up six feet of space.
If you have a grouping of photos look to balance them visually. Because we look from left to right keep the larger photos on the left and bottom. I find it helps to lay the photos out on the floor first. It helps to get them just the way you want them before hanging them and realizing you don't like the look. Another hint is to trace you photos on brown paper. Now you can us blue painters tape to hang the paper on the wall. This will let you move them without damaging the wall until you like the look of the arrangement. It will also make it easier for you to know where to put the hanging hardware.
That's a few hints to help with hanging your newly acquired art work. Now it's time to go hang some photos!