I love the symmetry, the fact that the pictures make the tv less of a sore thumb, and that the arrangement adds a ton of depth and texture to the wall.
Mrs. Limestone custom-ordered the frames from PictureFrames.com (I've ordered custom matting from them before and can also vouch for the quality) but you could recreate the look with cheaper frames from Ikea or the craft store if you wanted to spend less. She used black and white photo prints from her (envy-inducing!) travels. You could do something similar even with shots of plants, trees, or architecture in your neighborhood.
Kudos on an amazing job! See more pictures (and an animated gif of the hanging process!) on Brooklyn Limestone.