@Rob,
Unfortunately I doubt I’ll ever get chance to join in with this myself, but how about setting up some kind of a Corona dev challenges page, like Codepen has?
https://codepen.io/challenges
My thinking is that you could create a new “Challenges” category within the forum and every month post a new discussion within there, setting a new theme for Corona devs to submit entries to. Only Corona staff should be able to start new threads and perhaps also shut the comments off for older threads each time you post a new.
Then every time a new theme is started, write up a blog post about any notable entries from the last.
I don’t think prizes are needed - most developers would just be glad to get a write up on something they’ve written, and I’m sure at least some entries would be viable releasable games so it’s an opportunity to get some free exposure too. But mostly, it gives you something to blog about every month that’s genuinely interesting for the community and doesn’t need much time to think up.
There are a few designers who post artwork to these forums too. Entries could be either code or artwork. It’d be really nice if designers posted artwork for developers to use in their dev entries - see who comes up with the best use for a particular graphical asset. Again, this gives exposure to said artists too - I’m sure people would join in.
Perhaps not too late for Easter to be the first theme either, if you want to give this a shot?