Hello,
If you just want to display the image for vendors and not the main vendor, you will have to add a condition to check the vendor ID ; just like it's done for the address display.
Regarding the way to display a vendor image, the best is to use the HikaShop image helper.
You can find various examples in HikaShop or HikaMarket.
Maybe the most suitable would be in the "vendormarket / view.html.php" file ; for the display of the vendor page.
That view is reading a lot of parameters (from the HikaMarket config) in order to set-up the getThumbnail call.
The usage of getThumbnail is almost mandatory because you want to have some consistency in the vendor images ; so the invoice would have always the same "render" even if one vendor uploaded a bigger image than the others.
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.