A noble attempt, but does not work for me.

Image Saver does not appear in the context menu for large tiled images, such as when zooming in on
https://artsandculture.google.com/asset/el-si-pronuncian-y-la-mano-alargan-al-primero-que-llega-they-say-yes-and-give-their-hand-to-the-first-comer/NAHi_9r0H5PfJw

(Note, you'll need to use "Shift+Right-click" to get Firefox's context menu since Google is silly and disables right-click on its artsandculture site.)

A different extension (Search by Image) does allow me to right-click and "Show Image" in a new tab. Each tile is a 512x512 PNG that I can save, but it is tedious doing them one by one.

The description of Image Saver says that it can save "any images" not normally downloadable, so I mistakenly expected Image Saver to give me the option to save all the tiles at once. Unfortunately, since the Image Saver option does not appear in the context menu, it cannot save even a single tile. I hope the author updates this extension so that any and all data blobs can be saved easily.

I have not found any image that this can download that I couldn't download regularly. The context menu item does not show up any time I've tried to download an image I can't normally download. For example, eBay auction photos.