I've been using my own videos, but any good first-person video will work (cycling preferred, but jogging or even first-person automobile videos work well).
Technically, any video that is playable via a media player will work. The project natively uses the mpv media-player (mpv.io), though VLC (VideoLAN) integration is a priority.
For some ideas, query YouTube for "POV cycling" or "first person cycling."