Can you avoid using a large module and still get the functionality you need? Modules are saved in the image, and even after Delivery has gone through them to throw things out, they may still have a noticeable effect on the size of the delivered image. The fewer modules you use, the smaller the delivered size of your application.
Note: Some modules are built on top of others. If you load such a module into the image the others are loaded too. Pay close attention to these "hidden" contributions to image size by following the loader messages in the Listener.
LispWorks Delivery User Guide - 13 Dec 2011