^^If you use s18000rpm method, it will affect current tab (all pages you open on that tab or through that tab) only. But wont be consistent over sessions... If you use infra_red_dude's method, it will be consistent over sessions but will only affect one page.
@s18000rpm, I actually customise the toolbar to include the show images options dropdown list in the toolbar itself instead of going to the View button and then pressing the show images options list... I use it regularly, so it is important for me... If I remember correctly, it used to be on the main toolbar earlier but was pushed into the View toolbar sometime recently (prob. around 8.5 or 9 version)
Arun