I hadn't actually thought about what a roundel for Seasons of Discontent would look like, but something like that seems reasonable, unless I can find a easily identifiable and very relevant specific example I could use instead.
If you browse "Berlin unter Wasser" (Berlin under water), you can find a picture of Berlin TV Tower amidst of nothing but water. I actually thought of taking Berlin as a scenario in this round because more apocalyptic scenarios of global warming (as in Antarctica unfreezes in its entirety) may actually see the Berlin glacial valley drown whereas the neighbouring Barnim (northeast) and Teltow (southwest) plateaus may be spared.
I have an idea for The Locked Country: Whether it's your Jammu-Kashmir or Switzerland or Nepal or Bhutan... Tibet is called "the roof of the world", for god's sake. You'd essentially make a big-ass mountain and put the Potala Palace (former seat of the Dalai Lama in Lhasa, Tibet) on top of it. How you display the "lock" I have no idea, but gravity should be locking enough.
Maps In The Mirror: We see Nazi Germany (incl. General Government) from the backside as it looks into the mirror and sees itself as merely West Germany. A more humble approach would be the UNO Reverse Card.
The Weak Suffer What They Must: You remember my German refugee stamp.
Mind The Gap: Look at my profile, I've done a medal for myself in the mean.
Sunshine And Lollipops: Teletubbies landscape with a laughing sun.
The Last Straw: Either a powder keg whose ignition is already burning or a self-immolating man.
Diaspora: Dude, where's my bonsai tree?
Centenary: Make a decimal clock face with Roman numerals, I to X for the "hours" and X to C for the "minutes". The hands should look like one o'clock.
The Dust Has Settled: Run-off-a-mill before-and-after scenario.
Ab Urbe Condita and Greener Pastures: You have a golden milestone and a stork in your nest. Move on!