Hi, yes, you can edit your gpx files and set pure html inside your waypoint description, another guy uses this tecnique to show links and other stuff: http://www.gsnatisone.it/tracciati-gps/
this is a sample:
<wpt lat="42.438878" lon="-71.119277">
<ele>44.586548</ele>
<time>2001-11-28T21:05:28Z</time>
<name>Your Title</name>
<desc>Your html here</desc>
</wpt>
You can edit your gpx manually or use a gpx editor, as you like the most!
P.S. Remember to clean the plugin cache to get reload the file once you made changes to the gpx