The items should be more important than they are now. Rather than being (stat) boosters for a character maybe give them (more) tactical use in mid battle.
The badges and challenge don't work for me. I've got 4 or 5 bronze star costumers and over $130 in tips, but I still don't get the corresponding badge and card. Otherwise it's a fun game.
 "Doodle God"){kind=icon}
 "Kongai"){kind=icon}
 "Blocky"){kind=icon}
 "Papa's Pizzeria"){kind=icon}
 "The Endless Zombie Rampage"){kind=icon}