Hi,
When you edit a category in the backend of HikaShop, you can upload an image for the category.
For the moment you can just upload a new image but it would be possible to select an image in your existing images in a future version (which is be possible for products in HikaShop 2.1.0)
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.