I wouldn't say you are wrong, it does require an ....
executable file.
^The WMF format was developed to facilitate the exchange of graphics between various programs. It allows executable program code to be stored in a document's meta-information and then transferred to the recipient.
A weakness in the WMF rendering engine allows attackers to execute any code they want in the WMF files with user rights for the affected machine, the BSI reports. This weakness can be exploited using 'Enhanced Metafile' (EMF) files as well.
The security problem affects several Windows versions, including XP SP1, XP SP2, 2000 SP4, 98 and ME.
^
image virus
My experience dates back 3-4 years so they may have stopped a lot of this by now.