[ltk-user] Icons

I'm trying to add an image or icon to a menubutton (or regular button) and I don't quite get how it works. What does the first parameter of image-load represent (i.e. photo as in (image-load photo "x.ppm"))? Should I be working with bitmaps instead of images? How does the result of the load get assigned to the widget? And how does the :anchor or :justify get placed on the icon as opposed to the button text or the button itself? Is there an example of this anywhere? Thanks, Bill