ooobo's fork of nypublicradio's social-audio tool. Fork includes a live theme editor and custom background image uploading. Working ok (doesn't seem to have any performance impact). See the original repo README for instructions.
IMPORTANT NOTE: the larger the background image filesize, the slower the audiogram will generate. Resize the image before you upload it using the custom background image function! Anecdotally I found that a 860KB PNG would take >11mins to generate, while the 2KB PNG provided took ~1min to generate a 30 second audiogram.