An issue that arose when using the Google Structured Test Tool was the use of SVG images for the required image. After some digging, I found StackOverflow had the answer (https://stackoverflow.com/questions/35188719/svg-images-in-amp-article-microdata) only it is not the accepted answer that provides the exact details. Google doesn't allow SVG as an image property type, even though schema.org doesn't state SVG not being an accepted format. This really creates a problem with the reason I was using SVG for article images in the first place. They scale! PNGs don't. Guess you can't win them all.
While experimenting with scalable vector graphics, structured data microdata and the google structured data testing tool, I ran in to an error that I am pretty sure wasn't there before. Looks like a good time to do some searching for answers.