Currently, if an emoji is used as a profile icon, the dock app icon has a white backgroundd added to the profile icon:

In the RC versions prior to the release of profiles, the emoji icons had a transparent background, making the dock experience arguably more visually pleasant:

A transparent background would make some emojis look silly (thanks eirk for the picture): 
The vast majority of emojis do not need a white background to display properly. Thus, I would like to suggest the following options for the profile icons in the dock app icon:
- transparent background
- white background
- a darker alternative to the white background (or even allow the user to pick the desired color using a color picker)