To make the shrimp: Combine the wine, mustard seeds, pepper flakes, bay leaf, 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 leaf.
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.