What else can I put on lettuce leaves and tunafish to make a healthy salad?

Slices of avocado

Sliced or crumbled hard boiled egg

Sliced or diced cucumber, tomato and red onion

Chopped pickles

Cooked Edamame (unshelled)

Broccoli and/or cauliflower

Snow Peas

Crumbled bleu cheese or feta

A little fat free italian dressing or some oil and vinegar (balsamic or regular)

Sliced red or white onion

Jalapenos

Olives

Capers

Mushrooms

Walnuts or pecans

Dried fruit, especially cranberries

Mandarin oranges

Sliced or Julienned Carrots

Sliced or Julienned Bell Peppers

Bacon

Croutons

As for dressing I'd say nothing too heavy. Try a vinaigrette or maybe an oil and vinegar combo.

You could put slices of tomato or some sweet corn. Olives would make good combinations too. Some mozarella or white cheese would be nice too. you could also slice some cucumber. Hope this helped :)

Boiled egg.

Onion.

Tomatoes.

Thousand Island dressing..

Diced hard boiled egg..

Sesame Seeds..

Milled--flaxseeds

Cheddar Cheese

Blue Chesse

...that's about all's I can think of.