I believe in the standalone there is a way to edit the customer images that's kind of glitchy. But standalone also has a frame-rate issue where you have to manually cap the framerate to 60... or else it goes through the roof.(300-1000 etc.)
For the Nvidia framerate, I think PitchBlackKnight said "Nvidia control panel -> Manage 3D settings -> 'add' Cowtastic Cafe -> change max frame rate to your refresh rate, or 60".
Aaand, the next update will (hopefully) have the ability to swap out the customer images natively if everything in the kitchen cooks properly.