Combine orzo, cucumber, onions and tomatoes in a large bowl.
Place dill, vinegar and mustard in a blender and blend until smooth. With blender running, slowly add olive oil and blend until emulsified. Season with salt and pepper.
Pour vinaigrette over orzo mixture and stir well to combine (you can save some of the dressing in a squeeze bottle to drizzle over salad before serving).
Gently fold in feta cheese.
Cook shrimp and use to top salad. Finally, drizzle reserved vinaigrette over the top. Garnish with additional dill.