I never actually considered SVGs for avatars, nor have I worked too much with them (I'm largely a backend dev). Some quick research shows it works just like other image files, so I'll take a look. I've never been great at working with images, so maybe you can recommend something with this.
Right now, when you upload an avatar, regardless of type, its shrunk to fit within 150x150. I did that so people who weren't good with images could use a larger file but it would be scaled down for resources to work well on the site. That being said, an SVG doesn't need to scale the same, as its a vector graphic. I could easily have some CSS set the max-height, max-width for SVGs only and then do the scaling for non-SVG files. Think there's a better solution?