I never use lettuce because I hate wet leaves, but there's no need for salad to include leaves. I just do vegetarian, but you could add meat.
I do a lot of "chopped salads," which is just chopped and shredded vegetables. My usual is any combo of peppers, cucumbers, cherry tomatoes, avocado, broccoli, cauliflower, green beans, sugar snaps, lentils, beans, roasted chick peas, roasted potatoes, shredded cabbage, kale, green onion, cilantro, parsley.
Or I can toss that onto a bed of seasoned brown rice, wild rice, millet, kashi, bulgur, sorghum, or quinoa, all of which are good cold. Throw in a hard boiled egg.
Or it can be tossed into a pita with tzatziki/hummus/etc.
If I'm really lazy, I'll just have a big bowl of raw peppers and cucumber, hummus and a hard boiled egg.
Lately I've had sweet cravings, so I have plain yogurt with homemade granola, banana and honey.