Hide Image Frame or Turn Off Image Border in AutoCAD - Remove Boundaries - YouTube
CLIP Command
CAD Forum - Seamlessly connected images by irregular clipping in AutoCAD (or LT).
Chapter 12: External References and Images. After completing this Chapter, you will be able to do the following: Working with External References Adding. - ppt download
How to control what you see by clipping xrefs and blocks - All About CAD