To start, preheat the grill to medium-high heat. In a small jar, combine all the vinaigrette ingredients except for the thyme. Shake the jar vigorously until the ingredients are well blended. Set aside 3 tablespoons of the vinaigrette for later use in brushing over the shrimp. To the remaining vinaigrette, add the thyme and give it another shake. Skewer the shrimp and brush them with the reserved vinaigrette. Grill the shrimp for approximately 3 minutes on each side, or until they turn pink and are fully cooked. Meanwhile, prepare the lettuce and place it in a large salad bowl along with the red bell pepper and red onion. Top the salad with the grilled shrimp and toss everything together using the remaining vinaigrette.