Both icon and banner are now supposed to be PNGs with transparency. If the banner or icon takes up the entire image (ie, it is completely rectangular or square), then there is no need for transparency; however, if there is any part of the image itself that one ought to be able to see through to a background, it needs to be transparent.
The banner should not be larger than 200 pixels in either dimension.
The banner and icon must have different file names.
