That's not quite what I mean, but I maybe this will work? Brute force it to find. I was hoping there might have been a better way to check
if ( my_config["enable_boxart"] == "yes" )
{
local surface_boxart = fe.add_surface( 480, 480 );
local boxart = FadeArt("boxart", 0,0, 480, 480, surface_boxart); // check here first
local boxart = FadeArt("flyer", 0,0, 480, 480, surface_boxart); // If nothing, then go here
boxart.trigger = Transition.EndNavigation;
boxart.preserve_aspect_ratio = true;
surface_boxart.set_pos(flx*0.35, fly*0.05, flw*0.40, flh*0.40 );
surface_boxart.rotation = 12;
}