I saw that Melange has a URL option. So you don't actually need to upload to there. Just add the Gerrit URL to Melange.
Can you explain this problem? What browser did you test in?
As noted in Melange and T52843: Use consistent preferences icon, there are two different gears. The other one is at Special:Notifications.
The background-image-svg mixin does not have the attributes specified for this icon, such as no-repeat, which causes something like this:
I will upload a full photo with correct icons in a moment. I was testing on chrome but had cache issues while editing. Screenshot taken in firefox, will take final screenshots in both browsers.
Also, removed Preferences.png in /modules/special. The iconsnow reside in /modules/icons as: