Request context: [[ https://upload.wikimedia.org/wikipedia/commons/c/c9/Ballot-sprite.svg | Loading SVG ]] as background image from [[ https://commons.wikimedia.org/w/index.php?title=MediaWiki%3AGadget-EnhancedPOTY.css&type=revision&diff=191359963&oldid=114497048 | this CSS file ]].
```
$ curl -I https://upload.wikimedia.org/wikipedia/commons/archive/c/c9/20160327111940!Ballot-sprite.svg
HTTP/1.1 200 OK
Date: Sun, 27 Mar 2016 13:25:03 GMT
Content-Type: text/html
Connection: keep-alive
X-Object-Meta-Sha1base36: k1h4wypkf9tobg8qw2dymx0qab6s6on
Last-Modified: Sun, 27 Mar 2016 11:19:42 GMT
Etag: 8a196dc538b917f2153323c7e91bd8ca
X-Timestamp: 1459077581.66301
X-Trans-Id: txb8a16672748b4be7a5baf-0056f7df2e
X-Varnish: 3801160535, 3256140095, 2826967039
Via: 1.1 varnish, 1.1 varnish, 1.1 varnish
Age: 0
X-Cache: cp1062 miss(0), cp3037 miss(0), cp3035 frontend miss(0)
Strict-Transport-Security: max-age=31536000
Set-Cookie: WMF-Last-Access=27-Mar-2016;Path=/;HttpOnly;Expires=Thu, 28 Apr 2016 12:00:00 GMT
X-Analytics: https=1;nocookies=1
X-Client-IP: 91.218.200.230
Access-Control-Allow-Origin: *
Access-Control-Expose-Headers: Age, Date, Content-Length, Content-Range, X-Content-Duration, X-Cache, X-Varnish
Timing-Allow-Origin: *
```
Expected: Content-Type: **image/svg+xml**
Therefore, I can't use uploaded SVGs as background images for POTY. Firefox simply doesn't display it. It says an error occurred somewhere on some background property but the developer tools are currently broken and do not display the correct location (always show something in OOjs UI).