The "Make a Sandwich Birthday Cake!" website.
It's basically what it sounds like...If you can't eat sugar or just want a healthier cake (or something whimsical to do with a sandwich), you make a stack of sandwiches with a savory filling, then ice them with herbed tofu or faux cream cheese or what-have-you, and decorate using slices of vegetables or edible flowers.
I think it's ingenious.
Some of the recipes and ideas provided on the website are non-vegan (but I think the idea is easily veganizable).
I haven't tried creating a sandwich cake yet, but I just might do it one of these days.
The bottom of the webpage also has photos of crazy elaborate garnishes, if you're interested in looking. Whoever did the site carved a bouquet of flowers out of a watermelon. Holy crap!