May I ask why you think it is due to the installation of McAfee? Please make certain you are current with all of your Windows Updates/Add-ons to include Internet Explorer. Even if it is not your Browser of choice. McAfee and other programs require it to be.
Knowing what your Operating system is, would be helpful also. Short of contacting Technical Support, which is available 24/7 Via Phone/Online chat being quicker. Services and Support for Home and Office There are lots of hits on this issue in Microsoft Forums.
This is just one of many Images are not displayed in Outlook 2010, Win 7 64 bit
All the very Best,
McAfee Community Moderator
I might add, it has been suggested that resetting your Browser to the "Default" settings in some cases resolves this issue. Just a thought....