In this example I have used the map of the Itasca demo of the Mapserver.
I have done only small changes to the map file.
The Itasca demo has (into the html file) the parameters of the path where to store the images:

IMAGEPATH "set in index.html"
IMAGEURL "set in index.html"

I have changed them as fixed path

IMAGEPATH "/tmp/ms_tmp/"
IMAGEURL "/ms_tmp/"

Than I have set as STATUS ON several layers for a better map.