Pat the shrimp dry and season both sides with salt.
Cut the peaches into thick wedges (6 to 8 per peach, depending on size).
If using large tomatoes, core them and cut them into wedges approximately the same size.
Thread the shrimp, peaches, tomatoes, and cubed bread onto doubled skewers, alternating as you like but beginning and ending each skewer with shrimp, for a total of 8 kabobs. Lightly spray with cooking oil.
Preheat the grill with high heat and oil the grates.
Grill the kabobs for 2 to 3 minutes per side, until the shrimp are pink and firm and the bread is lightly charred. The tomatoes may be bursting.
To serve, place the kabobs on a platter. Thinly slice or tear the basil and sprinkle it over everything with a drizzle of balsamic vinegar.
Notes
If using wooden skewers, soak them for 30 minutes before use.