Create and load a different image if the default image does not convey the required information. Use a web file format such as PNG, GIF, and JPEG that is a maximum of 1 MB to add an image that is 200 pixels wide by 133 pixels high. If the image is a different dimension, it is resized to 200 by 133 and may appear warped. Refer to "Edit item details" at http://doc.arcgis.com/en/arcgis-online/share-maps/item-details.htm#ESRI_SECTION1_D770A2AE32F647DCA47F48622D460B6D.