I do not report a bug actually but a suggestion to add a feature that exited in Ubuntu before introduction of Unity Greeter as login window: displaying user pictures in the login window.
It seems that as Unity Greeter runs as the lightdm user it is not able to access files inside a user home directory, which usually also includes pictures a user would choose as his/her picture in the User Accounts tool. I guess this is the reason why Unity Greeter does not display user pictures besides the user names.
This could be solved by creating a directory for storing user pictures so that Unity Greeter can access them. The following command illustrate creating the directory:
sudo mkdir /usr/share/unity-greeter/user-pictures/
sudo chmod a+wt /usr/share/unity-greeter/user-pictures/
Besides, Unity would need a means for copying the user picture file to the above directory. The following commands illustrate this task:
# get the user picture path from the right place
PicturePath=~/foo/bar.ext
# copy the file
FileExtension=`echo $PicturePath | sed 's/.*\.//'`
cp -f $PicturePath /usr/share/unity-greeter/user-pictures/$USER.$FileExtension
I am working on solving the same problem at office. I am trying to include a picture box sort of thing in the greeter box. Hope to come up with a solution very soon.