pretty up yukata

I bought a yukata 2 years ago when I was visiting Japan. This coming Sunday, my sister is going to wear it for photoshooting with her husband. Any accesory that can be added up to yukata? (eg brooch on the obi or pretty hair pin)

Of course you can if you want! but a yukata is a very casual outfit, more like a bathrobe. Some people do wear them outside for example in a hot springs resort while going from one onsen to another, or in their garden or even to shop at the corner store in their residential area. Also during a local street festival when dress rules are relaxed. I have seen people wearing kimonos (both sexes) in big cities but no yukata.

A lot of young girls today wear yukata in the city on summer weekends, so no problem about getting on the subway in them. They'd wear it in outrageous modern coordinations, for example with high-heel sandals and big earrings, so anything goes. But traditionally, you don't wear yukata with accessories other than perhaps things like netsuke.