Cream colored throw pillows and throw blankets will brighten the room, keep the leather from being overbearing, and will help balance the white of the ceiling so it isn't out of place with the warmer colors.
How To Create a Gallery Wall on a Budget - I was able to purchase IKEA Ribba frames in a variety of sizes for just under $200. My notes on the diagram above show the breakdown of sizes and associated costs. I bought 14 frames but used 13 for the collage. I decided to mix the wood and black and purchased half of each finish.