When the name of a raster image file is not sufficient to identify an image, you can add a descriptive name using the External Reference palette.
Image names are not necessarily the same as image file names. When you attach an image to a drawing, the program uses the file name without the file extension as the image name. Image names are stored in a symbol table; thus you can change the image name without affecting the name of the file. Up to 255 characters are accepted for image file names. In addition to letters and numbers, names can have spaces and any special characters not used by Microsoft. Windows. or AutoCAD for other purposes.
If you attach and place images with the same name but from two different directories, numbers are appended to the image names.