Image based on node taxonomy terms
I used to use the Taxonomy Image module. It has full views integration as well.

Features:

    Image configuration happens within existing admin/taxonomy menu structure.
    Admins can add custom tags to &lt;img&gt; markup when displaying images.
    Allows one-to-one term-to-image relationships.
    Allows many-to-one term-to-image relationships.
    Admin-permitted users can disable the images.
    Administrators can force images to be a standard size.
    May use the ImageCache module if it is available.
    Works with Views.
    Utilizes core file.inc and taxonomy.module APIs.
    Small module with specific, focused functionality.
    Add-on modules that virtually eliminate the need for theme changes.