A: Hi there.
Glad you like what you see.
At this moment, custom backgrounds are in the pipeline, but have not been implemented as of yet :
https://sinosend.com/roadmap/p/ability-to-customize-your-download-page
Please add your feedback here, sorry to disappoint, we would love to support photographers like yourself, but rotating custom backgrounds isn't currently planned.

Please do leave your feedback in the portal, we'll see if we can get around to it.