How do I make Messages.app override a contact's buddy icon? I have a Jabber account configured in Messages. When other people on the server change their buddy icons, the changes are pushed to my machine. I want to override their icons and force Messages to display an icon for them that I select.

From the buddy list, right-clicking on a contact brings up the context menu option "Show Contact Card". This launches Contacts.  But I have a custom image set for them and Messages is not displaying it.

I recall iChat having an option to specify using a custom image rather than the pushed image, but I can't find anything here.

This is for Messages version 7.0.1 (3314) on OS X 10.8.2 (12C60).
Select a buddy in messages, go to the Buddies menu, then click on 'Show Info'.
In the "Info for  window, go to the tab on the very right called 'Address Card'. Next to their picture, is a checkbox for "Always use this picture". I believe this is the option you want.