Often the new tunings come about because I'm trying to play something in a way I hear it on another instrument and I can't. It could be an Irish fiddle decoration, or the way a Chinese Erhu can bend a long way on every note.
I figure out what's missing, scribble down on a piece of paper a tuning or construction that might work to get that sound im after, and head to the workshop to make a test harp. It will generally go through quite a few versions before arriving at the best compromise between easy playability, good sound and achieving the new ability I sought.
To answer your question, trying to emulate what other instruments do on the harmonica is often a good way to learn. The PowerBender will allow you to play Richter harp licks in a new way, but listen beyond harp players to guitarists, sax players etc and see if you can grab a bit of their special magic and transfer it to your harp. Some will work, some won't, and even the stuff that works you will need to tweak here and there to make it sound sweet.
But that's one good way you can get fresh ideas and slowly create your own style.
Another is exploring unusual positions: they take you away from cliches and uncover some surprising hidden gems. Here's a sample of 11 different keys on the PowerBender, all without overblows:
https://youtu.be/GNoxhd0EdLU
If that sounds worth exploring, theere is more detail with example licks and Tab in the PowerBender book/CD:
http://www.brendan-power.com/instruction.php