Now I understand what you mean - I thought you meant the top menu icons
I have installed the latest 'release candidate' version which resolves this issue with placeholder images.
Category Blog sub-categories not yet fully implemented
this isn't an error message - its basically saying that we haven't implemented the code to allow you to customise the sub-categories links you can get at the bottom of the category blog page. That will continue to be controlled by the normal Joomla output until we implement this.