Sure you can provide an image as request body, but you could already do it with b64 query parameter. If you try hard enough, you can poorly use any proposed standard. GET with query parameters already is opaque and makes cache busting trivial.
Query parameters are length-limited, because HTTP URIs are: https://www.rfc-editor.org/info/rfc9110/#section-4.1-5. There is no expectation for arbitrarily long HTTP URLs to be functioning.
Query parameters are length-limited, because HTTP URIs are: https://www.rfc-editor.org/info/rfc9110/#section-4.1-5. There is no expectation for arbitrarily long HTTP URLs to be functioning.