Heinrich Lefler and Joseph Urban were Austrian born illustrators and stage scene designers who collaborated as well as working independently. In addition, Lefler was a painter and Urban an architect, and they were brothers-in-law.
They were active in the late 19th and early 20th centuries. I have not idea how to sort out who did what and which illustrations are collaborative, as they are usually shown and listed together.
Their illustrations often incorporated Art Nouveau influenced patterns, both within and surrounding the images.