You have several options.
First there are some templates built specifically for HikaShop out there. For example :
hikashop.vjtemplates.com/
www.websitetemplates.bz/hikashop-templates.html
Then, you have templates built for Virtuemart. They should also work with HikaShop although some of the customizations which are specifically for virtuemart won't be applied to HikaShop.
And then you have all the others joomla templates which will also work. Rockettheme has a lot of nice templates, however, some of the features in them can be a real pain as they create javascript problems so if you don't want to have problems, you might want to avoid that (there are several threads on our forum about that)...
