https://xenforo.com/community/forums/resource-and-add-on-requests.68/ or https://xenforo.com/community/forums/custom-service-development-requests.69/
You could see if @sonnb could do that with their gallery addon. I really enjoy their addon and they seem open to customizations.
I afraid that it is not possible. It must be in core of XenGallery. Standalone must integrate with either XenGallery or XenForo Media Gallery