Phil Gyford describes a technique for removing the Movable Type command image buttons. Although I don't use Mozilla, I've been wanting to do the same thing just to reduce the page size. I didn't change the top images (in logonav.tmpl), but I did change the side bar (in mininav.tmpl): modified mininav template file.
Removing MT Image Links
Mobile Websites
As a side project, I maintain a popular list of mobile websites on cantoni.mobi.