Thanks for taking a look, I'm wondering if anyone might have any suggestions or ideas on how to handle this scenario.
I'm using https://cesiumjs.org/Cesium/Build/Documentation/SingleTileImageryProvider.html to overlay an image on cesium, but the images don't lend themselves to the Rectangle required by the Single Tile Imagery Provider.
I'm debating skewing the images and adding padding to make them rectangular, or switching to using a polygon primitive and using an image material (although I'm not sure how to tell the image material which corners of the image should go where).