I don't know if there is a site just like gamiss but if you want to buy clothes with bitcoin you must exchange it first to $ and paypal as a payment method. Because most of the online shops do only accepts payment with paypal or any other authorized web site. If you are not unable to find some other site like this, well try my suggestion and use virwox for it.Indeed you can , and it depends on your country . In Indonesia , we have tees.co.id .
This site has bitcoin as the payment , so you can buy clothes much easier . And it allows you to design your own clothes.
For the shipping , i'm not sure about worldwide shipping you can contact tees support for further information.