I've created a different loading.bmp for iGO in the most popular resolutions - 480_272 and 800_480. You can find out how to use them here http://www.navitotal.com/showthread.php?9475-How-to-change-loading-screen-in-iGO Primo can be found in the data.zip in the ui_igo9 folder. Scroll down to the loading.bmp.
Important: It is important to backup your data.zip and branding.zip from the original program on your SD card BEFORE attempting any editing. You would also delete the save folder but I also suggest ...