Who knew that Facebook had a secret artistic side? Mathias Bynens did, at least. He recently noticed that Facebook and Instagram automatically turn many public photos into ASCII art just by adding a file extension to the end of the web link -- ".html" if you want a color image, or ".txt" if you'd prefer it in black and white. I've tried the trick with a few of my photos (see above and below for examples), and it definitely works -- the results have a great lo-fi vibe that could work well for a Facebook background image or even a poster.
As to why Facebook is doing this? It's not clear yet. This could be for some as yet unknown app or service, or it could just be engineers having fun with code. We've reached out to the company, and we'll let you know if it can solve this mystery. In the meantime, have fun. It's a simple way to inject new life into photos that might otherwise gather virtual dust.