Veneers should be stored in a cool dry environment, preferably out of direct sunlight as this causes them to bleach-out. They should ideally be stored on flat, horizontal shelving under light weight to keep them flat. Remember that veneers are hygroscopic, so the RH of the air will ideally need to be controlled. Contact with walls should be avoided. For best practice advice on veneer storage and handling refer to W. A. Lincoln "The Complete Manual of Wood Veneering" ISBN 9 780854 420407. This is a standard text for woodworking technology and one of the very few texts available on industrial veneering (e.g. he deals with subjects such as veneer stitching, etc) as opposed to the DIY/home craftsman approach so often encountered.