Reduce the size of the image by shrinking or write out a new (reduced) image file. Either way - if size matters and you feel like you have to dig into bootstrapping an own Smalltalk system based on Squeak you should have a look at this post from Eliot.
There you will find code that will produces a headless 57k image with a few basic classes as a proof of concept. Interesting!
Reminds me on the minimal image experiment from the past that was able to compute 3+4 which was only a few kilobytes in size. Nobody was able to see the result since it was instantly garbage collected ;)