The base path seems wrong. It doesn't make sense that Tremulous was installed into /usr/games, it was probably /usr/games/tremulous (I am unfamiliar with OpenSUSE, however, so I cannot say for sure). Try to run Tremulous from /usr/share/games/tremulous. This error is caused because Tremulous cannot locate the game data.
Also, this command may help in locating the install directory:
locate map-atcs