gecko/mobile/android/app/profile/extensions/feedback@mobile.mozilla.org/skin/overlay.css

#tool-feedback {
  list-style-image: url("chrome://feedback/skin/beta-hdpi.png");
}

#feedback-feedback-happy {
  list-style-image: url("chrome://feedback/skin/happy-32.png");
}

#feedback-feedback-sad {
  list-style-image: url("chrome://feedback/skin/sad-32.png");
}