Every time I see a well done diptych, I love 'em. The motivation to do them on my own escapes me, though. I also love looking at other people's photos. I thought I could suggest combining a couple of my photography loves and do some collaborative diptychs.
There are endless variations of how it could play itself out. But the way I picture it is I would submit a photo to another user. They could ruminate over it and then either go through their back catalog or go shoot something new to pair with it. The person who offers up the first image is completely passive in the process. The final decisions made about crops and any fine-tuning are up to the 2nd photog.....so obviously. Basically once they see the image, they incorporate it into their own vision of the finished diptych. So this isn't for everyone...... and obviously it's meant for every photograph.
This is just meant as a measure of general interest in the concept.... and maybe discuss any ideas any other interested parties may have before starting something.
If you're scratching your head and wondering what a diptych is, it's something like this (pardon my example....it was the first one I ever did.....I like the idea, but the execution leaves a bit to be desired). They don't need to be equal sized photos....and the don't need to be the same subject matter....sometimes contrasting shots working great, too.....
old-timey soda by Lukinosity, on Flickr