Problems making an animated stereo panorama

I want to make a short (looping) animation comprising a simple animated sequence set against a static background and to view it in an Oculus Quest 2 VR headset. I have designed the background image and have rendered it as a stereo panorama. I can load it into the headset and view it using Pigasus.

Problem is, the background is a complex model and takes few hours to render as a static image. I feel sure there must be a way to develop an animated sequence in which the complex static view serves as a background while the (much simpler) dynamic elements are rendered on top.
Can someone suggest how to go about this?

Thanks