Jester - you have the image right there, and of the correct 400 x 234 size. Just change it to a .gif image and you're sorted. Replace the existing ===BMW=== .gif image using NavTweak in the file detailed by the link and instructions from KiwiJochen in the first post of this topic.

Obviously you will have to manually edit the software version to force an update, as Jochen did by using 6.40 in the above info. Once you've made all the necessary adjustments burn it (Mode 2 - important for a MK III unit!) and load it. If you don't understand any of what I've just said, or the advice given originally by Jochen, or with burning images, I wouldn't attempt it without step by step assistance.