Hey there @camodonnell,
You can add the image above the header by
1) Uploading the images to Shopify CDN (Settings > files)
2) Adding an <img src="YOUR SHOPIFY CDN IMG URL">
3) Adding styling to it to make it full width and height
But the above steps will show the same image on all pages. To be able to display different images on different pages you can use Shopify schema to make the theme section and then put an image of your choice on each page via theme customizer.
Thanks for the appreciation. I've sent you an email please check.