I can change the Decal Types settings in Revit Arch 2011 but not 2013. I looks like I can change them but if I click OK and then open the Decal Types dialog box again to check the settings are back to default. I'm trying to change the Finish and Luminance. I tried it in several files with the same images (png and jpg) but it only works in 2011.
I filled out a trouble ticket with AutoDesk. The Development team indicated that there needs to be a code fix, however they did not provide a time frame or a work around. I will keep you posted.