User blog comment:Rappy 4187/Technical Update: April 20, 2015/@comment-1192804-20150421130738

If you load a custom background through Special:CSS (to bypass the 300kb limit in Theme Designer), it doesn't seem to work anymore.

What's the new code?

Before it was:

body { background: #000000 url(http://url.image.png); background-position: top center !important; background-repeat:no-repeat !important; background-attachment:fixed !important; background-size: cover !important; color:#FFFFFF; }