Sometimes last year some people connected to the user interface design of GIMP have set up a discussion blog for brainstorming ideas about user interface features.
http://gimp-brainstorm.blogspot.com/
You find everything there - from small changes to radical new redesigns. The rules are simple - you just send in your image. All the text you need to explain your idea has to be on the image. And, as everything is CC, you can take an image, modify and comment it and put it back into the pipeline.
Both images are from the site, the top one made by J.D. Chambers , the lower one by “Tobias”.