// Random switch
random_switch (FEAT_TRAINS, SELF, random_sgs){
1: return spritegroup_sgs1;
1: return spritegroup_sgs2;
1: return spritegroup_sgs3;
}

switch(FEAT_TRAINS, SELF, switch_subtypes_sgs, cargo_subtype){
0: return spritegroup_sgs1;
1: return random_sgs;
2: return spritegroup_sgs2;
3: return spritegroup_sgs3;
return spritegroup_sgs1;
}

switch(FEAT_TRAINS, SELF, switch_sgs_x, cargo_type_in_veh){
return switch_subtypes_sgs;
}

......


graphics {
        default: switch_sgs_x;
    }