yourATCstore Halloween ATC Postcard Collage Sheet. This Halloween Collage Sheet features 4 vintage postcards that are the size of ATCs. 2 of the ATCs are ghostly cemeteries and the other 2 are just fun ones to play with. Use the vintage images to create your ATC postcards or use other images too from the other Halloween Collage Sheets that we have to offer. This matte finish collage sheet is professionally printed and comes in a crystal clear bag for protection. Each collage sheet measures 8 1/2" X 11" and is acid free.