Cook spaghetti according to package directions. Drain, rinse with cold water, and drain well. Transfer to a large bowl. In a medium bowl, whisk together Italian dressing, cheese, seeds, seasoned salt, paprika, garlic powder and peppers until well blended. Stir in cucumber and onion.
Pour over spaghetti and toss lightly to coat evenly. Cover and refrigerate at least 2 hours or up to 24 hours. Garnish with tomatoes and parsley sprigs.