Is this royal icing painted, or gold to begin with? If it's painted, it's done very well! If it's not, how do you get your royal icing that shiny gold color? (I can get my icing gold in color, but it doesn't have that shiny luster.)
The shine is from luster dust. They probably used a tan or golden frosting base and then did the luster dust overtop.
Check these two sites out for more information.
It's painted. You can dry dust or you can mix the dusts with lemon extract [I find this best for smooth, adhered paint] or high % alcohol like vodka, gin, or Everclear [the best].
If it's going to be eaten, then the paint should be made using edible luster dust made of FDA certified color [see the list of companies below] like those shown in the sweetambs.com link or #1-3 in the bakinginheelscookies.com link [#4 & #5 are not edible].
If you're certain that it won't be eaten, then you could use metallic highlighters, as long as you are certain that the decorations will be removed and not consumed.
FDA advisory against using non-toxic dusts directly on food:
One beautiful cake if its not a dummy.
Thanks for the input! Even if it's a dummy, the decorating is gorgeous! :)