After looking around and seeing the lack of variety in MLP-related personass for FireFox I decided to try and fix that. So here's a nice Rainbow-Dash-themed persona, a bit on the colourfull side and quite bright.
This is mainly aimed at 1980x1080 monitors so if you're on a lower-res monitor you won't get RD's cutie mark.
Rainbow Dash - http://yourfaithfulstudent.deviantart.com/art/Flying-Rainbow-Dash-276296528
Cutie Mark - http://browse.deviantart.com/?qh=Â§ion=&q=rainbow+dash+cutie+mark#/d3e1glv