The capacity of a rack-mounted storage library having a media element handling assembly is expanded by mounting a panel segment to a rack side such that the panel segment faces the rack interior. At least one of media element housing cells and a media player are supported on the panel segment such that the cells and the player face the rack interior. The library capacity is increased by mounting another panel segment having cells or a player to another rack side. The panel segments are mounted to the rack sides independent of one another or are connected together prior to being mounted to the rack sides. The handling assembly moves through the rack interior to load media elements held by cells into a player. The panel segments may be mounted to the rack sides at the same or different rack length positions.