there's quite a few different bits of software for grabbing full-size pictures from gallery's,
a couple of my favorites are:
Bulk Image Downloader
http://antibody-software.com/web/index.php
(will try and Download everything on the page)
Interactive downloader
http://homepages.nildram.co.uk/~goldbug/
(is a lot more versatile and lets you pick and choose which pictures to Download -
highlight then 'Drag & Drop' the thumbnails into Interactive downloader)
(perfect for grabbing stuff from my thread ... 'inserts blatant plug'
https://www.forumophilia.com/topic53998.html )
the browser Firefox has various Extensions / Add-ons that will Download pictures for you -
worth checking out
(Google: Firefox Image Grabber downTHEMall)