I found out today that the Internet Archive has a process that runs automatically when files are uploaded that delays the contents being available, sometimes for quite a long time.  Files are called "derived", and the process is documented here:

https://archive.org/services/docs/api/ias3.html

The API notes that the delay of the uploaded contents being available can be avoided by adding a x-archive-queue-derive:0 header to skip the deriving process.

https://archive.org/services/docs/api/ias3.html#skip-derive-process

This is a suggestion to add this header to the upload so that the images are available faster, which will improve the user feedback and confirmation that image uploads were successful when adding new cover art.