Wait a minute - are you trying to put scrolling text over an image? You can do that with layering (right other people?!? I could be wrong), but I don't think that Front Page has a specific way to do that (the only times I've ever gotten an image over an image was on accident, and I'm not sure I could figure out how to recreate that situation). If your just trying to add scrolling text, goto Insert->Active Elements->Marquee. Hope that helps a little.
FrontPage 2000 has an absolute positioning feature for images that will let you layer images on top of images. Get familiar with the fp help files that come with the program, they show you how to do it. You can put a component on top of an image if you use the image as a background image (again, layering).