GaveUp:
just a few points:
1) compressing/resizing images is going to be the most effective.
2) apache already comes with
mod_deflate which is a very effective HTML content compressor - but this works (and others) are only really useful on html/js/php content that can be compressed - not images.
3) the page might expire, but the image is still a seperate HTTP request - there's not large quantities of time spent loading HTML.
4) this might have a small improvement - but if the load average of the system is not high, then the cause is likely to be elsewhere - like big images.