I think you need some finely minced onion or green onion, a squirt of Worcestershire (serves same function as anchovy puree which you could also use), some lemon juice and/or zest, a shot of hot sauce and maybe a bit of mustard. Mild fish and potatoes need some help not to be bland.
Epicurious has a Tunisian Fish Cake recipe if you want to go exotic. It is good when you make it, even better the next night. I use less garlic than it says, add some minced anchovies and use crushed Saltines or breadcrumbs instead of matzo meal.
