This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
According to the api for javax.imageio.ImageIO the read() method would return null if there is no registered reader that can decode the image file. So you need to find a reader which will read that type of file and make sure it gets loaded.