Images inserted in AutoCAD have a border known as a Frame.  You can turn this frame on and off by using the TFRAMES command (an Express Tools Command that Toggles Frames on Images and Wipeouts).  You must have frames toggled ON if you want to select an image.  Before plotting you may wish to toggle frames off.  TFRAMES will do the trick.

As an addendum to the topic here is a tip from the CADalyst newsletter (2009-08-17)

Turn On (or Off) Image Frames: If you use images in AutoCAD (or any AutoCAD-based software) you may not want the frames around the images to show when printing/plotting the files. Set the system variable IMAGEFRAME to 0 (zero) to turn off the frames. Set it to 1 to turn on the frames (and to print them). Set IMAGEFRAME to 2 to turn on the frames in AutoCAD but not print/plot.

For your convenience here is some other info from the AutoCAD 2010 help file.

The FRAME system variable overrides the IMAGEFRAME setting. Use the IMAGEFRAME system variable after the FRAME system variable to reset the IMAGE frame settings.

Note: Normally, when image frames are not displayed, you cannot select images. However, the IMAGECLIP command temporarily turns image frames on.

To add to the heap of commands that turn frames on and off this one comes with a twist. Are frames in front of or behind the image? AutoCAD Map has the command MAPIFRAME to display the frames or not and the MAPIOPTIONS command to set the behavior within the Raster Extension dialog. The AutoCAD Map help file offers this advice under the topic “Changing How Image Frames Are Displayed.”

For images you insert with Raster Extension, you can choose to display the image frame in front of an image, behind an image, or you can hide the frame. When the frame is behind the image, you can still select the image by selecting the frame. However, if you hide the frame, you cannot select the image by selecting the frame.

These options do not apply to images you add with Data Connect.

Note If you use the Toggle Frames command to hide frames, and then redisplay them, the frames appear in front of the images.

And the command that has the final word on frames is the FRAME system variable. The AutoCAD help file reveals the behavior of the FRAME.

FRAME Turns the display of frames on and off for all external references, images, and DWF, DWFx, PDF, and DGN underlays.

The FRAME setting overrides the individual IMAGEFRAME, DWFFRAME, PDFFRAME, DGNFRAME, and XCLIPFRAME settings.

Now you have the commands to control image frames so they can be on or off, front or back, plotted or not plotted in a variety of combinations.