Hi,
I don't know which script you are using but the variant images are in an hidden div and copied in the main image div.
But in your case, these images have an opacity set to 0 ; it is something that not made by HikaShop.
It results that when the images are copied, the opacity stays and you can't see the images, because their are just no visible.
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.