I've updated the Windows CE 5.0 Image Diff tool - The main change is to allow you to select an XML template file manually - here's the issue...
If you examine the filenames of all the MSFT shipped platform templates (Internet_Appliance.xml, Tiny_Kernel.xml etc...) these filenames match the name displayed in the Platform Builder workspace file - here's a snippet <Workspace PlatformName="vsdemo" Template="Internet Appliance"
Note the only difference is the addition of the underscore in the name, and the addition of the .xml filename extension.
It would appear that there are a number of 3rd party Platform Wizard files, and these don't conform to the (totally unwritten) standard of matching the wizard xml filename to the name included in the Platform Builder Workspace file.
So, when this happens the CEImageDiff tool would just give up and thow an appropriate messagebox on the screen - Now, the tool throws a messagebox on the screen and then allows you to choose which wizard xml file to compare against.
You can get the new tool from here - Note that you need .NET Framework 2.0 to use the tool.