Clean an interior brick wall with a stiff brush and soapy water. Steel brushes will work for interior brick walls -- on exterior brick, steel that becomes embedded in the mortar can cause discoloration as it rusts.
Paint interior brick walls in minimalistic colors such as white or cream. The rough texture of the brick will add enough visual interest to the wall that no other color is necessary. Egg shell paints should be used for walls with an especially rough texture.
Repair damaged, crumbling walls by digging out the old mortar and installing new mortar. This process is known as repointing.
Decorate a brick wall with photos or paintings that are minimalistic in nature. Black and white photography in a simple white mat and black frame is appropriate. Don't decorate the brick wall with anything that will visually compete with the texture of the brick. Avoid paintings that have many bright colors, or intricate patterns and designs.
Hang pictures on the wall with metal fasteners that clip directly to the bricks. Avoid nailing holes in your mortar or brick.