Thank you for the tip. I was going insane!
To help others find this helpful post, I'd like to point out that the beta period is over and the offending app is now called "Tetra Lockscreen" by Microsoft. The solution is still this:
* Swipe right, scroll down to Settings
* Click "lock screen"
* Click "photo" under the word Background
* Choose "Bing"
* Lock your phone and unlock it.
You may now go back and re-select "photo" from the lock screen menu if you wish
To help others find this helpful post, I'd like to point out that the beta period is over and the offending app is now called "Tetra Lockscreen" by Microsoft. The solution is still this:
* Swipe right, scroll down to Settings
* Click "lock screen"
* Click "photo" under the word Background
* Choose "Bing"
* Lock your phone and unlock it.
You may now go back and re-select "photo" from the lock screen menu if you wish