Desktop theme referred to the appearance of a TARDIS console room. Entering the Tenth Doctor's TARDIS, the Fifth Doctor noted that he had changed the desktop theme to "coral", which he found worse than the "leopard skin". (TV: Time Crash)
When the War Doctor, the Eleventh Doctor, and the Tenth Doctor entered the Tenth Doctor's TARDIS, it caused the Desktop to glitch, turning it into each of the other Doctor's control rooms. (TV: The Day of the Doctor)