Just throwing this out there from a girl's perspective in the customizing world: Nail Art!
Tiny little studs and shapes designed for nails can look pretty cool as decorative buttons and clothing details. Dirt cheap from eBay and you get hundreds/thousands in one little baggy
The silver metallic round ones are usually my go to buttons- even if I have to paint them sometimes, then glue on using tweezers and a toothpick.