PREHEAT grill or broiler.
MIX oil, 2 tablespoons pesto, garlic and shallots in medium bowl. Add shrimp; toss to coat. Marinate in refrigerator.
CUT bell peppers in quarters; grill or broil until skins blister. Place peppers in bowl; cover tightly with foil. Cool until peppers can be handled; remove charred skins.
CUT cooled bell peppers into 1 1/2-inch squares.
THREAD bell peppers and marinated shrimp alternately on skewers; discard any remaining marinade.
TRIM ends off of bread and discard; cut bread in four 1-inch-thick slices. Grill or broil until golden and crispy. Spread remaining 1 tablespoon pesto evenly on bread slices.
GRILL or broil shrimp skewers until shrimp are cooked and turn pink.
PLACE 2 slices of grilled bread on each plate. Remove shrimp and peppers from skewers and arrange on top of bread. Garnish with fresh basil sprigs or with an herb bouquet. Drizzle with lemon juice; season with sea salt.