How can I host website images on a non-web-server?

We have a client that has an (apache) webserver and a storage server on the same network. Due to the sheer volume of images they would like to host the images on the storage server but still be able to pull them up on the website.

Is there a way to setup Apache so that it maps the IP address/directory on the storage server to itself?

We are using PHP as our server-side language, if it matters.