Tasty sauces/condiments for salmon burgers?

How about going the mustard route? A little mustard or mustard-based sauce, tomatoes, & a few sprigs of arugula. I love smoked salmon toasts done this way.

chimmichurri cut with some yogurt or a mild aioli or even mayo if it comes to it.

I like wasabi mayo.

How about a tzatiki sauce?

I like the aioli idea. Maybe a lemony aioli and some roasted red peppers along with some mild arugula.

I really like aioli, avocado and bacon on my salmon burgers, and I know a lot of people poo-poo iceberg lettuce, but i've had it with salmon it does offer a refreshing note and cut the richness of the fish. Another idea is to serve the burger with some sort of slaw on top that would additionally offer some bright flavors against the fish, especially one with lemon or lime juice and zest in the dressing.