Having retrieved the attachment to your BlackBerry and opened it for viewing, use the trackwheel to scroll through the document. If you see an image in the document, scrolling, while using the trackwheel will highlight the image in grey. When the image is highlighted, press the Trackwheel and select Retrieve from the menu. When the image has been retrieved, press the Trackwheel once again and you will be given the options to Zoom In and Zoom Out, allowing you to make the image bigger or smaller, as desired. You can continue zooming in on the image until it is of a suitable size for you to view on the device.
After zooming in, if the image is now bigger than the screen size, you can use the Trackwheel to scroll up and down on the image. To move left and right, press the Alt key and use the Trackwheel to scroll.