I noticed that the Team flair on meta uses the Discourse SVG icon.
I managed to upload a custom SVG sprite in my theme to get access to custom icons for group flair, but it doesn’t seem to allow you to use the SVG icon at full flair size, it assumes you want it as a small icon inside the flair circle.
Only other option is to upload as an image (jpg, png etc). It doesn’t allow SVG.
It would be nice to know how it’s been done on meta.