There should be an option to set the display size of an image to zero

[Marc Feeley]

Images added to a buffer with put-image always occupy an area in the buffer 
that is equal to their size.  It would be nice to allow the image to be 
overlaid over or under the text which would allow annotating the text with 
arrows, bubbles, etc. This could be as simple as indicating a zero width and 
height for the image (for determining the placing of text around it), but using 
the actual image size for displaying it on the screen.

Marc Feeley