Check out this post - https://answers.splunk.com/answers/287949/what-path-do-i-use-to-add-new-files-images-and-fon.html
The answer applies to Quick State as well. Just make sure any image you want to use exists in:
/opt/splunk/etc/apps/quick_state_app/appserver/static
For example. to use the file preview.png, use this eval statement:
eval img="/static/app/quick_state_app/preview.png"
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