This video will demonstrate how to customize Pie charts and Table visualizations from the classic dashboard user interface and edit the Simple XML source code. This is a follow on video where similar customizations were created using Dashboard Studio builder    • Splunk Dashboard Studio Pie chart and...  

You will also see how to include images into an HTML panel for both Classic (Simple XML) dashboard and Dashboard Studio builder.

Splunk documentation links:

Splunk Classic (SimpleXML) Dashboard Chart Configuration Reference:
https://docs.splunk.com/Documentation...

Splunk Answers How to assign colors to slices of a pie chart on a dashboard when the number of slices vary?
https://community.splunk.com/t5/Dashb....

Splunk Classic (SimpleXML) Dashboard use HTML file in a dashboard panel:
https://docs.splunk.com/Documentation...