Ivory Brony shared an original composition called After We're Gone. It was inspired by the fan fiction Growing Up, which you can read here if you're interested.
You can find the song on Soundcloud. Give it a listen—it's really nicely done. The piano rhythm is very peaceful and relaxing. Ivory Brony pointed out that although the song is short, it loops well.
Many thanks to Ivory Brony for sharing this original piece!