Since the Tilapia has a nice flavor on its own you can just season it with lemon, garlic, salt and pepper and the flavor is great.
If you want a big bold flavor try the chili-powder or Cajun marinades.
With the bolder marinades, I find I don't need salsa, just vegetables and cheese.
I like to marinate the fish for at least 8 hours, bake the fish fillets whole, and then cut them after they are cooked.
Serve the tacos with your favorite garnishes.