I may be in the minority here, but I LOVE the challenge of working within a short allotment of pages. One of the things I have to be mindful of in longer works is to be aware of unnecessary elements (dialogue, narrative, plot). It may sound good but I have to ask myself if it is necessary to moving the story along, especially with so much pages to work with. I credit this "get to the point" training for the improvement of my pacing.
To answer your question, I don't think there is any particular idea that works best for a short format story. The same can be said for any length work. I believe it just comes down to execution.
I actually made an exercise for myself writing one page comics (See here:ONE PAGE COMICS ). For exercises like those I'll seriously just let a random thought pop in my head and build a story/scenario around that. For instance, with the one page comic Sepulcher, I looked in my standing lamp and saw a whole bunch of dead moths. I then brainstormed on how I could execute the theme (futile existence).
If anyone else is interested in short format (1-20 pages) themed challenges, then let me know. I'd love to see what everyone else comes up with for themes. I think it would also be good discussion for encouragement and improvement among our community.