A content-type of "application/json" is returned whenever requesting a public image hosted by dropbox. I've tested with both a png and jpg
$ curl -I https://dl.dropboxusercontent.com/s/REDACTED/name.png?dl=1
HTTP/2 200
accept-ranges: bytes
cache-control: max-age=60
content-disposition: attachment; filename=name.png
content-security-policy: report-uri https://www.dropbox.com/csp_log?policy_name=blockserver-usercontent ; sandbox allow-forms allow-scripts allow-top-navigation allow-popups
content-security-policy: form-action 'none' ; report-uri https://www.dropbox.com/csp_log?policy_name=blockserver-noscript ; script-src 'none'
etag: REDACTED
pragma: public
set-cookie: REDACTED; Domain=dropboxusercontent.com; HttpOnly; Path=/; SameSite=None; Secure
x-content-type-options: nosniff
x-server-response-time: 123
content-type: application/json
accept-encoding: identity,gzip
date: Mon, 03 Oct 2022 21:02:59 GMT
server: envoy
strict-transport-security: max-age=31536000; includeSubDomains; preload
x-robots-tag: noindex, nofollow, noimageindex
content-length: REDACTED
vary: Accept-Encoding
x-dropbox-response-origin: far_remote
x-dropbox-request-id: REDACTED
