Attached are the files for an stand alone demo of the mentioned feature (it refers to images which are available as assets already, in my SS site; so this should not be a matter of not found resources on server).
I also needed to change the configuration of the editor, to allow me putting custom attributes as those in the sample; but I finally made it (again, the source of the generated pages do show desired custom attributes).
Any ideas? I am almost sure this is not exclusive of the theme I am using, but mentioning just in case.
Thank you a lot in advance folks,