Here is the art viewer.
With it you can easily view all the arts in any desired detail and export them as bitmaps (optionally using batch save).
In the latest version it also displays unit-borders and position lights (thanks to Hooman for the info).
There isn't much to tell, so you may just download it.
The archive contains the viewer with the dll and three info files about the structures used by the prt and by op2 to manage the arts.
Batch save accepts commands like 'img()', 'pic()', 'frm()', 'grp()' or just numbers like '0-100, 200 300' to save the desired object type.
(Be careful using batch save with multiple groups or frames as images, since they'll be split into single images which can easily end up as A LOT of files. Instead it is often sufficient to save whole frames, unless you want to use the images to rebuild the arts yourself.)
It also treats all unexspected chars as whitespace.