By default this works correct automatically. Incoming requests that are not recognized by Wicket are just passed through.
However, there is an optimization that is not very well documented. When you already know that certain paths are never going to be handled by Wicket (for example because you configured a servlet for them), you can tell the Wicket filter to ignore those paths in the same file as where you define the servlets: in the web.xml.
Example web.xml configuration:
<filter>
<filter-name>wicket.filter</filter-name>
<filter-class>org.apache.wicket.protocol.http.WicketFilter</filter-class>
<init-param>
<param-name>ignorePaths</param-name>
<param-value>images/,rest/</param-value>
</init-param>
</filter>
Note: make sure the paths are comma separated without additional whitespace.