I noticed the user account picture is not displayed correctly while using start10 ..
I am developing small application to retrieve user account picture and faced the same problem my work around was to copy the user account picture from the system to my application folder during form activate and deactivate and name it with the: "username.bmp" and then load the copied picture from my application folder to the picturebox in my application and that's it.
If the user change his/her account picture I always copy user account picture to my application folder and override existing file during form deactivate and activate