Missing toolbar images after upgrade
After upgrading EPiServer from 5.2 to 5.2 SP2 the ImageVault images were missing in the EPiServer Xhtml Editor. 
It turned out that the images is placed in the App_Themes folder and is unique for each EPiServer version.
Copy the images (ImageVault* and Meridium*) from Program Files\EPiServer\CMS\version\Application\App_Themes\Default\Images\Editor
to the version you upgraded to.
Nov 06, 2009
To avoid this from happening you could make a vpp to the iconbase and and place the images somewhere you have better control over the path.
Have a look at this thread where it was discusses.
http://world.episerver.com/Forum/Developer-forum/Developer-to-developer/Thread-Container/2009/4/Override-IconBase-location-CMS5/
Regards,
Morten