This error is hard to reproduce. The number of images
is not critical. The reuse of the image names when recreating the images may be.
create a canvas widget
create three gif images with "image create photo"
create three image items on the canvas.
delete the three images
re-source the script above.
do not call update or update idletasks between
image deletion and re-creation.
The panic appears to happen at the time the images are recreated and before they are added to the canvas although this cannot be confirmed.
It is likely that the cause of the error is the fact that the original images are deleted via an idle callback which has not fired by the time they are re-created and the new images that are recreated using the same names are being deleted by the idle call back which now fires for the three original images.