If you want a stronger bench, you must get strong triceps, deltoids and lats, not just strong pecs. Of all the assistance work you could do, developing stronger triceps will probably have the greatest impact on your bench press. Work hard on the basics, including various types of heavy extensions and close-grip bench presses (flat and incline).
Strengthening your front delts will also bring major improvements to your bench press. Assistance work for front deltoids should include military presses and all kinds of front raises (dumbbell, barbell, with a 45 lb. plate, etc.).
Your lats are involved in the bench press to a greater degree than you might think. Your lats help you maintain your arch and stabilize your torso. They also help you lower the weight by providing a "cushion" to lower against and push from at the bottom. The best assistance exercises for lats are rows, rows, and more rows! Barbell and dumbbell rows are the best assistance exercises for the bench press because they train the back through the same horizontal plane as the bench press
Still nothing about the lats being built from the bench press... directly. Nada. Zilch. Cero. 0.
Beautiful topic, this.