There is a temptation, with an equipment rack in a studio, to pack the entire rack full of gear, top to bottom. But remember that most gear needs steady airflow to maintain a suitable operating temperature. Tubes, for example, put out a lot of heat. This heat must flow out of the item to prevent overheating. If another piece of gear is positioned directly above a heat-producing device, it will also be absorbing the heat from that device.
For that reason, it’s a good idea to leave blank rack spaces above pieces of equipment that get warm or hot. It takes more rack spaces to do this, but your equipment will last longer and perform better if it is kept cool.
For aesthetic concerns, there are solid and mesh blank rack panels that can be installed into empty rack spaces. These will hide unsightly cable mess while still maintaining air flow and providing a nice look from the front of the rack.