Imageshow sometimes will show this error

Error loading images. One or more images were not found.

Cause

When you change an image in a slideshow via ftp, Imageshow's cache will not updated and will still use the old version of the file and there is no way to refresh the cache via joomla or Imageshow.

This issue does not occur if you elect to use the original image or if you upload an imagewith a different name, it only happens when you overwrite an existing image.

It is mainly thumbs that are affected and some types of slider, other wise full image is used.

You have to manually delete the cache

Imageshow does not register it's cache in Joomla's cache manager so is very difficult to clear the cache of imageshow. You have to delete the files manually via ftp so the changes are refelcted and It stores them here:

images/jsn_is_thumbs/images/modules/member-of/test-image.png
images/jsn_is_thumbs/images/modules/main-slider/
images/jsn_is_thumbs/images/pages/building-and-property-maintenance/gallery/

You can remove and then re-add the image which would have the same effect.