For a few years earlier in this decade I worked in the opera department at Malabar, a costume house in Toronto. I had access to literally thousands of items ranging from the times of ancient Egypt (Aida) to the late 19th Century (La Boheme). Naturally, I shot some photo reference so I could use them to eventually make some mock opera posters and other paintings/illustrations. (although, I'm not entirely sure that this costume was actually from Faust)
I designed the layout, added the text, and created the "flames" in CorelDraw and then processed the photo (to make Mike the model look extra devillish) in Photoshop.
When building something digitally, the "size" kind of becomes irrelevant, because the final print size of the image is only limited to the resolution of the file.