Apple distributes their "add to wallet" images as SVGs which is great, but if you want to add it to an email or anything else that has issues with SVG files you're going to need a PNG (to maintain transparency around the rounded corners). Unfortunately there are a LOT of these images needed to support the various languages.
Converting these to PNGs is not as easy as you'd hope. Problems encountered:
- imagemagic produces unusably bad images (mostly just black) even though it's theoretically calling rsvg-convert under the covers and calling that directly works fine.