Allright, so some good options here!
browser.cache.compression_level;5 – This setting determines whether Firefox compresses the data in the disk cache, reducing the size of it.
browser.dom.global_scope_pollution;disabled – Disable the more agressive emulation of IE's "IDs directly accessible in the global scope" behavior. I have
no idea what this means but I had to create a new boolean.
browser.fixup.alternate.enabled;false – Disable Firefox/TenFourFox/Mozilla adding "www" when trying to resolve a domain name.
image.cache.size;132768 – Changing the cache size for images.
image.http.accept;image/png,image/*;q=0.1,*/*;q=0.1 – Network headers. You are essentially telling the browser to accept images equally when loading.
image.cache.timeweight;4000 – Time to discard decoded images from cache.
There are a few more I tried, but if you follow the link you can see the rest of the entire list. I'll post the rest I tried later. That's it for now.
@Altemose, you're up man!