hi

// if you need unique decal shadow for the mapent:
// put it into mapent action:
set(me, SHADOW);
you = ent_create( "name_of_decal_shadow_image.dds", nullvector , NULL);
set( you , INVISIBLE | PASSABLE );
my.shadow = you;

// else if you need a general shadow
// put it among varialble declarations:
ENTITY* ent_shadow_rot =
{
type = "name_of_decal_shadow_image.dds";
}
// put it into mapent action:
set(me, SHADOW);
my.shadow = ent_shadow_rot;