Windows 8 is supposed to get a new feature in Taskbar which adds User Image right next to where your clock is. I am sure it will not be just an image but there will be more shortcuts or app integration will be there but we will need to wait till it comes out.
Now if you do not want to wait and want to have this Windows 8 User Tile to your Windows Taskbar, AngelWZR @ deviantart has developed a simple application, which does it. All you need is to launch the application and it will add a picture right next to the clock. Also when you click on the tile, it will give your shortcut to control panel, Your Account on Windows, Lock, Switch or Log Off.
By default this application does not pull image from your user account, call it a drawback, but you can edit a simple configuration files available with the application file and add your image path.
You will have to close and restart the application to reflect the changes.