Grabbing images for a NN to process

Hi all.
Noob here.
I’m hoping to use top-down images from Cesium to train a neural network for a client application. I’ll be classifying the features in a separate operation. But before I do that, I need to gather the highest rez images I can from Cesium of a specific area, bounded by 4 points for which I have the LatLongs.

What I’m hoping for is a way to mark on the terrain (In Cesium Stories maybe? Not sure) with a 4-sided shape that defines the boundary, then output images from within that boundary. Some overlap is fine.

I’m hoping for a way to automate this, though I’ll do it manually if I have to.