I know this is an old post, but for those who run across it now...This is now possible in Splunk without a separate app, just need to create your own custom renderer.
Here's an example from the Splunk Dev Documentation: http://dev.splunk.com/view/webframework-codeexamples/SP-CAAAE5Q
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I don't believe so, at least, I haven't seen a way to do it. Latest version has updated the text to be "No Results yet found," until it finishes the search and then displays "No Results found."
Would be much better to have a blank map with notice overlaid with the "No Results found."
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