Standby Mode asking to unlock to view photos. How to disable?

This just spontaneously happened with my phone, as well. Had it set to show a digital clock and the weather in Standby, but last night, I got this unlock to show photos screen instead, it won't switch to the red mode until it's unlocked (so the white clock lights up the room), and I can't figure out how to get it back to clock+weather - long press on the screen just lets me change which photos display.

I have a second MagSafe charger that still shows what I want - simplest solution might be to switch the chargers, but since it happened without any input from me, I'd like to know how to change it in case it does it again with the other charger. Crazy that we can't change anything about what shows in Standby mode unless it's in Standby mode, and interaction is severely limited in that mode.

Edited for solution: the "photos only" mode is a separate screen (the second of three). The mode I was used to (widgets) is the first screen, swiping from right to left gets to the photos screen, and another right to left swipe gets you just the clock (swipe from left to right to go back through the modes). I must have inadvertently swiped the screen, but perhaps the iPhone should detect if there are no lights on in a room and not show the photos-only screen if the room is dark.

Unlock it. You really don’t want someone who finds your phone to turn it horizontal and see your private photos.