I previously posted an (https://johnkiv.us/2013/01/23/clearing-flipboard-image-cache-on-ios/). Unfortunately, that procedure is no longer valid in Flipboard 2. Fortunately, the new procedure is much, much simpler:
1. Tap the red bookmark / ribbon thing in the upper right corner.
2. Tap on the gear icon in the upper right of the “My Flipboard” panel the slides out.
3. Choose “Settings” from the popup menu.
4. Scroll down to and tap “Clear Cache” at the bottom of the settings window.
That should do it.[^f2017].
[^f2017]: Be warned, the cache clearing process appears to take a long, long time.