I put shredded cabbage, broccoli and cauliflower (usually just one of these items) on quesadillas to add a nice crunch.
I add grilled mushrooms to my homemade baked macaroni and cheese recipe. It sounds odd, but it adds a whole other flavor dimension that is incredible.
As per tasting this concoction at a restaurant, I add mayonaise and peanut butter to my veggie burgers, along with the onion, lettuce and tomato. It sounds very weird, but it is tangy and adds a slight Asian flair/flavor to it.
I make a killer breakfast wrap with a flour tortilla filled with crumbled feta cheese, a dollop of orange marmalade and some chopped hazelnuts.
I make a pannini style sandwich (that I bake in the oven) with fresh mozzarella cheese, sundried tomatoes and arugula.
I like pickled jalapenos on my pizza.
And as per @KatetheGreat‘s standard cheese sandwich (why is that weird?) I like to add Fritos to that sandwich!
P.S. How come you decided to give up vegetarianism? I got more ideas for snacks and stuff if you are now eating meat. I based all my answers on that other thread with the idea that you were still veg.