Saving your application standalone is only the first step towards delivering a satisfactory image. The next step is to try and make it smaller.
An entire Common Lisp system, and other supporting code, remains in a standalone image delivered at delivery level 0. A good deal of this can usually be removed.
What can be removed depends on the needs of the application. Few applications use all the facilities in the basic image. For instance, if the application does not use any complex numbers, all the code in the image for working with complex numbers can be deleted.