public List<String> getImageMimetypes() {
        return getParameterValues(IMAGE_PARAMETER);
    }
Returns a list of all image mimetypes declared as supported within the
tunnel request.

@return
    A list of all image mimetypes declared as supported within the
    tunnel request, or null if no mimetypes were specified.
guacamole/src/main/java/org/apache/guacamole/tunnel/TunnelRequest.java