In my opinion the most usefull environment options are
  • SDL_VIDEODRIVER=driver name
    SDL_AUDIODRIVER=driver name
    SDL_VIDEO_CENTERED=
    SDL_VIDEO_WINDOW_POS=x,y or center (where x and y are window coordinates - topleft I suppose)
Here
you can find all other options. Note that on Windows SDL_putenv must be called before SDL_init
When complete if I post up some source of a Lua and SDL test could someone try to cross compile it for Linux and see how it works.
I can test it, no problem.

I just wish I knew why SDL didn't select the fastest context it could by default.
I think that it is impossible for SDL to detect the fastest driver. And by common sense directx should be faster.