1. A method for detecting a demountable accessory in an image-forming device, the method comprising: capturing a first image using an optical sensor associated with a print platen of the image-forming device, wherein the print platen is to receive a substrate and the optical sensor is to capture an image of an item on the print platen; carrying out an adjustment action by a handling mechanism of the image-forming device, the adjustment action for adjusting a position of a substrate on the print platen; capturing a second image by the optical sensor; analyzing, using the controller, the first and second images to identify displacement; analyzing, using the controller, at least one of the first image and the second image to detect an accessory identifier; responsive to the analyzing, determining the presence of an accessory and classifying the accessory based on the detected accessory identifier.