MAC offers two colors for their iridescent powder; Golden Bronze and Silver Dusk. It's a loose powder that is so versatile you HAVE to own both! Lol.
First you can wear it by itself, on top of your make-up, mixed with foundation/moisturizer, and can be worn any where on your face or body. Just don't try this technique, if you do- use the powder sparingly not a 50/50 mix. The color for both is pretty concentrated, so a little bit goes a long way. I like to use the powders in a C-shape by each eye and a bit on top of my cheeks for some extra sheen on nights I go out.
It's so extremely shimmery and adds just a bit of fun to any make-up look. Plus, I think it photographs well in pictures as well. See? That extra sheen on my cheeks is the bronze powder. I mostly wear just one of them at a time, but sometimes I'll put the bronze on my cheeks with a bit on the tip of my nose, then the silver in the C-shape.
Have you tried MAC Iridescent powders? What highlighters do you use?