Everything about Modding the game, from new courts to the modifications of the player & tournament bases (and including all the bugs they may be creating ! )
Downloaded Modding TEM2 SDK, created only those folders I was interested in in my TE4 game folders and if I remember well the only thing I changed were the names of some WTA tournaments (e.g. French Slam to Roland Garros, UK Slam to Wimbledon etc.).