When a supporter has multiple connected social media accounts, but a FaceBook account with restrictive privacy settings, the null FaceBook profile image will overwrite the working Twitter/LinkedIn images. It would be great if those images would instead serve as fall-backs when that happens. Also, sometimes socially matched profiles will return a zero-state (e.g. egg) or broken image link picture as the avatar — it would be great if we didn't treat those as legitimate profile pictures, and instead returned the default empty profile picture.
Alex! Great suggestion (and timely considering that I'm sure you know that Twitter images aren't working).