Heat oven to 350°F. Wrap tortillas in heavy foil and heat in oven for 10 minutes.
Meanwhile, prepare the salsa by combining tomatoes, cucumber, scallion, cilantro, lime juice, and salt in a bowl. Set aside.
In one bowl, toss green beans with 1/2 teaspoon of fajita seasoning.
In another bowl, toss shrimp with remaining 1/2 teaspoon of fajita seasoning.
Heat olive oil in a large skillet over medium-high heat.
Add seasoned green beans to the skillet and cook, stirring frequently, for 3 minutes.
Add seasoned shrimp to the skillet and cook, stirring, for 3 minutes more or until shrimp turn opaque.
Remove tortillas from oven and assemble tacos by dividing the shrimp and bean mixture between the warm tortillas.
Serve immediately with the fresh salsa.