If the game uses the standard configure build system you use the the following options on your CDBS debian/rules:
DEB_CONFIGURE_EXTRA_FLAGS := --bindir=/usr/games --datadir=/usr/share/games
It is very common to have games splits in 2 packages, the main package which usually contains the games binaries and other architecture dependent files, and the -data package which contains architecture independent files like images, sounds, music, such allows to have a single larger data package and just single per architecture binary packages.