well its not quite as simple as changing the media, becuase you still have to change how it is used
effectively with something like making the Quake engine, basically the engine provides the entire atmosphere - you then use a scripter to tell it how and where to use the media.
really if you were to make something like Quake, what i'd recommend is you make an editor like QuakeC ... so you have the basics to work from, but then you program in your own effects ... so like
v_weap.01 { `//<<darkbasic effect code>> }
and it'd then compile this into a darkbasic source which is used by the game, but should be in a compressed format so that source code is safe from each other and people who just wanna ripp off other games
however having an addon wouldn't be too hard to do if like you added an entire pack (^_^)
maybe i'll ask my brother to include this within his DarkBasic FPS engine - we've got a bet on about him being able to remake a decent FPS in DB without external help
Tsu'va Oni Ni Jyuuko Fiori Sei Tau!
One block follows the suit ... the whole suit of blocks is the path ... what have you found?