There's another stack overflow post that has an excellent solution.
It doesn't seem to be Tomcat specific, is simple, and works great. I've tried a couple of the solutions in this post with spring mvc 3.1 but then had problems getting my dynamic content served.
In brief, it says add a servlet mapping like this:
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>/images/*</url-pattern>
</servlet-mapping>