document recommended image dimensions; fixes #50
document recommended image dimensions; fixes #50

neicnordic/neic.no,neicnordic/neic.no,neicnordic/experimental.neic.nordforsk.org,neicnordic/neic.no,neicnordic/experimental.neic.nordforsk.org,neicnordic/experimental.neic.nordforsk.org