kins73, The image layout and dimensions are not the same for all firmware. While on some firmware menu images can be single files on others they can be made up of 4 -5 separate images that fit together to create the menu. So the theme you are trying to load may be for a different firmware layout. Not all firmware is suitable for the iPod style menu either as it requires the whole image to change from menu to menu, on some firmware only parts of the image change.
Upload your original firmware to
www.sendspace.com and leave a link and I will check it out and let you know what themes will suit your firmware best.