I made an update to my Base Master Page today that moved the PlaceHolderLeftNavBarTop content placeholder from the hidden ASP Panel at the bottom of the file to an appropriate place in the left navigation area.
The content page (\12\Templates\SiteTemplates\SPSMSITE\default.aspx) that controls the profile/public page of My Sites adds the profile picture of the user to the left navigation bar via the PlaceHolderLeftNavBarTop content control. To show this profile picture in your custom mater page, you need to include this content placeholder in your code.