You can change the drilldown elements in a visualization, when editing a visualization, you can also choose to "Show Data values". If you want to know more about those, you should download the "Splunk 6.x Dashboard Examples" app for good examples.
But if that doesn't do what you need, you'll have to work with javascript to get it done. For a starting point, look at the Dashboard Examples app, specifically Table Icon Set (Rangemap). Then if you are feeling up to it, you can look here: http://dev.splunk.com/webframework
... View more