The amazingRody Zakovich and I presented at the Tableau Conference last year in Las Vegas. It was a great session and we were pleased with the big turnout. Our session was on how to create custom charts in Tableau. Really our session was about how to create anything in Tableau by following three basic steps:
Plot Points Everything is a scatter plot
Connect Points Use the marks shelf (color, path, etc)
Format Points Add context and style
You can watch our presentation here. If you want to reverse engineer what Rody and I did we have posted our workbooks to Tableau public (Adam's slides).These workbooks have step by step walk-thrus of how every chart we demoed was created in Tableau.