Seibert was MTV's first creative director and guided its original voice and visual identity, creating hundreds of promotions, advertisements, and station IDs for the channel, and responsible for a rethinking of how television channels promoted themselves as "brands." He also commissioned and approved the mutating MTV logo (designed by the Manhattan Design collective, which included his oldest childhood friend, Frank Olinsky), despite network executives objections to a logo that did not remain constant. He led the team that developed "I Want My MTV!", one of the most famous advertising campaigns of the late 20th century.