Every time a frame's image changes, Boords saves it as a revision, so you can always get back to an earlier version without starting over.
Generate, restyle, reframe or drag in a new image, and each one is stored automatically.
Revisions show up in both the storyboard edit view and in the editor. In the editor, you'll see the full history as a row of thumbnails, and clicking any one of them sets it as the active image.
You can also lock a revision to protect it from being overwritten. Handy when a frame has been signed off and you want to make sure it stays that way. Revisions can be unlocked, but you'll see a warning when you do so. All lock and unlock events are tracked in the team activity log.