We are all familiar with the very primitive technique of squinting at a piece of work in progress to get a better idea of the general composition, geometric shapes, and combined overall colors.
I suppose the brain can sometimes miss the forest for all the trees (and other little details).
I don't know of any digital art program with this feature but I think a digital squint function would be nice. It would prove more reliable and consistent than manual squinting. Essentially it would display a full screen view at the same magnification that the user is currently using and at the same canvas position but with a certain kind and amount of blur (customisable by the user). Circular and gaussian would be my choices. There should also be an option to calculate this in the backround when there are spare cycles, so that when the shortcut key is pressed, the squint is that much quicker. I prefer the idea of a press and hold squint although a toggle squint would be OK...
A smaller virtual resolution could also be set to make the calculation quicker (instead of blurring the 5000x3000 image, another image say 500x300 could be continuously updated in the background and then blurred for the quint, and scaled up for appropriate display. This low resolution (percentage) to use the squint could be user customizable.
There are a lot of potential ways to implement it, and I think this feature would be a novel and useful one which could help with some color and geometry problems someone new to digital art may have.
it might even get some reviewer comments...