spriteset groundsprite {}
spriteset spr_coal { /* 2 real sprites here*/ }
spriteset spr_lumber {}
spriteset spr_pass {}
...
spriteset spr_mail {}

spritelayout station_layout {
  ground { sprite: 0; }
  building { sprite: 0; }
  building { sprite: 1; }
}

switch(FEAT_STATIONS, chose_building_sprites, cargo_type){
  COAL: spr_coal;
  WOOD: spr_lumber;
  PASS: spr_pass;
  MAIL: spr_mail;
  spr_coal;
}

switch(FEAT_STATIONS, station_chose_graphics, extra_callback_info1){
  0: groundsprite;
  chose_building_sprites;
}
switch(FEAT_STATIONS, station_cb_switch, current_callback){
  0x14: return 0;
  station_chose_graphics;
}