Through much(!) trial, error and tribulation, I've found very good success
using the following "Set options" settings for ImageStation to get full size
pictures.  NB: these work *only* for members whose photos are free to the
public, not requiring an upgraded/premium ImageStation account.

First, click a thumbnail on an index page.  You should arrive at a page
address similar to the following:
<http://www.imagestation.com/album/pictures.html?id=[numbers]&idx=number>.  Copy
this as the starting address but use an asterisk(*) in place of/after the
idx=.

Select Set options.

Use the following Scan Rules:

+*.css +*.js -ad.doubleclick.net/* -mime:application/foobar
-*.gif -*.jpg*[<58] -*.png -*.tif -*.bmp
-*/*thumb*
+*/.jpg.orig.jpg

On the Limits tab, select a Maximum mirroring depth of 3;

Build: html in web/, images/other in web;

Spider: no robots.txt rules;

Experts Only: For Primary scan rule, select Store non-html files; Travel mode
- Can go up and down; Global travel mode - Stay on the same top level domain.

That pretty much covers it.  Using these values should get you only the full
size pictures from an ImageStation album.  Unfortunately, the images will be
downloaded with nonsensical file names which you may have to or want to rename
to make a sensible display sequence order.