To make the shrimp: Combine the wine, mustard seeds, pepper flakes, bay leaves, and lemon in a large saucepan. Add water to fill the pan two-thirds full. Bring to a boil over high heat. Add the shrimp, and cook for 3-4 minutes or until the shrimp have turned pink and are no longer translucent in the center. Drain and cool. Discard the bay leaves.
To make the herb-dill dressing: In a screw-top jar, mix the olive oil, red wine vinegar, water, basil, dill, garlic, mustard, and onion. Shake well.
Place the shrimp in a large bowl and add the dressing. Toss well, cover, and refrigerate until well chilled.
Serve the shrimp mixture on romaine lettuce leaves and surround with the tomato wedges and mushroom slices. Garnish with dill sprigs, if using.