How do I redirect a Read More link to another URL in Showcase Image?
You can use the path-redirect module to forward the URL in the "read-more" link to any other internal or external URL.  If you forward internally, you need to use the "node/123" system URL and delete the alias for the node you are forwarding from, before you setup the redirect.

If you point at the read more link you'll see its node or alias in the lower left hand corner of your browser.