I know this is a rather subjective question, but what does everyone think is most essential to creating a good diorama?
In my opinion, composition and story are most important. They're really what set dioramas apart from a car on a decorated pedastal (Nothing against them. They're just not quite the same thing). Having a sense of motion and a sense of activity really bring a diorama to life and help make it memorable to the viewer. It can be difficult to capture, especially when you're starting out, but even small attempts can make a big difference. Making sure the diorama base isn't too small is something else that makes a huge difference. I know it's really tempting to cram as much as you can into a base (There's space and it's there! You can totally fit that in!) but I've found that a bit of negative space makes the chosen elements stand out since they're not crowded out by extra items.