Not reallly possible as the files will be on the CD. The only way I know to make them really hard to pinch would be to integrate them into a Macromedia (Shockwave Flash) presentation with nav control - that way the images would be embedded in the flash file and not copied to the CD as seperate files.
I would also think about watermarking them with your name / date and contact email for example. This means that you will be able to identify them as yours if ever you see anyone using them.
The problem with CDs is that you can always copy from them but not always to them......
Hope this helps (watermarking can be done with most competent graphics packages - photoshop / fireworks etc)
Have fun.
Rich:drive: