We're still using Cognos 10.x here, and I don't have a direct answer as to whether a single shared network location for images can be made to work, but I can offer the solution I've used in our multi-server environment, based on IBM's tech notes on the "missing images" in output issue.
I always use the relative path "../images/[imagename].jpg" when adding images to a report (have to edit the property if I browse to select). I copy any new images into the primary Content Manager's /images directory, then drop it onto a small .bat file I wrote to copy the image out to the /images folders on all three dispatcher servers in our environment (note that just having it on the CM's won't do).
It works just fine for us.
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Michael Walter
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