Hi,
With the current version of HikaMarket, it's not possible.
We started to work on the feature, to let the users upload the vendor image during the registration but I got some issues related to the upload folder and the uploaded content.
So there is still some code in HikaMarket to provide that feature but there is some missing code in order to make the feature completed.
The main point is that, when you perform a vendor registration, you might not have a Joomla account ; so you can't know where to upload the vendor image (because you do not have a vendor yet).
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.