I'm using a custom theme in windows 7 and when I'm using the theme no profile picture is shown in the start menu. Or any other picture occurs when hovering over Docs, Pics, etc. The theme I'm using is called PlastiQ aero and you can find it here:
To change your picture, go to control panel - users - change picture.
I'm not sure what you are looking for regarding a picture hovering over docs, but..
Go to Control Panel - Folder options, view tab
-uncheck always show icons, never thumbnails
-uncheck display file icon on thumbnails
-check show preview handlers in preview pane
If the file view behavior is completely out of whack, you can click on 'restore defaults'