If it has the .gz suffix you mailed your Actions, not the actual picture. This is a zipped file, and has to be unpacked to be used.
Actions are useful if you have a Mac and download the Brushes Viewer from their site. It allows you to replay the painting's creation on the Mac. If there is a way to import the actions back into Brushes on the iPad using Mail, I don't see it. Brushes doesn't appear to register itself with Open In as compatible with .gz or it's own .brushes extension. Maybe it would work through iTunes. They have a manual on their support site that you can download and look through.
If you were just trying to mail the picture then be sure to use the Mail Image and not the Mail Actions choice.