Based on a graph image posted by Sol Amour in http://dynamobim.com/forums/topic/the-best-question/ , I was able to create this graph that creates a list of all Filled Regions in a Revit file. (Thanks for the help!)
Originally, I tried to set the Categories node to FilledRegion, and pass that through the All Elements of Category node, but that resulted in an empty list.
Changing the category to TextNotes resulted in a list of Text items in the same Revit file, so I am wondering why setting the Category to FilledRegion fails. Did I do something wrong in my graph, or does this just not work for Filled Regions?