Put 1 tablespoon olive oil in a small skillet. Add onion and celery, stirring until they begin to wilt. Add artichoke, season with salt and pepper, and sauté about 3-4 minutes.
Set aside to cool.

Split avocados and remove pits. Use a large spoon to remove the flesh without breaking the shell, reserve shell. Coarsely chop avocados, place in a large bowl and toss with lemon juice to prevent darkening.

Set aside 4 whole shrimp, chop the remainder into bite-size pieces and add to avocados. Add cucumber, tomatoes and artichoke mixture. Coarsely chop herbs and add all but 1 teaspoon to the bowl.
Salt and pepper to taste.
Drizzle with vinegar and olive oil.
Toss to coat all ingredients.

Serve
Mound 1/4 of salad into each of the avocado shells and arrange on 4 plates lined with lettuce leaves.
The presentation is nice with avocado shell but you can just use a nice salad plate if you prefer.
Top each portion with the reserved shrimp, remaining herbs.