I love the Sriracha/Mayo combo for smoked eel. Anyway I think you might appreciate this, I was making pasta salad with crab meat and mayo and I mixed in some chinese chili oil (aka mongolian fire oil) with the mayo and it blends wonderfully. You might want to try that combination for sushi sometime.
Also: I love making desert rolls. I mix in a little coconut milk with the sushi rice and candy up sesame seeds by mixing them with syrup. The inside of the roll are long slices of mango, so it's similar to that great mango desert you can get at most thai, philipino and malasian restaurants.