Can a vegetable plot/permaculture garden be beautiful as well as super productive? Are there examples of any such gardens in existence?
Gaia's Garden by Toby Hemenway has some photos.
What you can do is use decorative garden design PRINCIPLES, but use food-productive PLANTS.
I'd encourage you to poke through Ros Creasy's website:
She lives/works out of Los Altos in the bay area, and her entire garden is chock-a-block full of beautiful edibles. Here is a video where one of the Dave Wilson fruit tree nurserymen visits her home:
She doesn't exactly fit under the permaculture label - she tears everything up twice a year and has a part-time gardener helping her every day - this is her livelihood, after all. But she is definitely an edible landscaper, and has some lovely examples of perennial edibles throughout her garden.