In Chrome and Firefox describing an image within the <defs> tag and referencing it from a path shows an image. Unfortunately it doesn't in Safari. Here's an example URL to base off of: https://jsfiddle.net/jonobr1/fofL6984/
Created attachment 317989 [details] Screenshot of Chrome and Safari rendering
I updated the Fiddle. The issue was that I defined the href without `xlink`. Sorry for the false alarm!
Closing out.