Changing unit art

[JonS1]

Lowlander,
there are a couple of components that must work together to display images.

1) the scenario file (*.scn) calls for units from the OoB based on ID numbers.
2) The Order of Battle file (*.oob) which - among other things - uniquely identifies each unit, and identifies the paticular portrait graphic which will be displayed for each unit when selected in-game.
3) The portraits (*.bmp) are the images displayed.

For your purposes, the important ones are 2) and 3). The reason the Atkinson images you refer to aren't being used is because the OoB file being used is not calling for them.

In this case. You can
EITHER
go to the OoB file, and change the name of the graphic called for by a particular unit to the one you want to use
OR
go to the bmp files and rename the files to the ones being called for in the OoB file.

Be carefuil though - it's fairly easy to completely bollix this, and end up with completely the wrong image being displayed, or no image at all. On the other hand, fiddling with the OOB, SCN, and BMP files can be immensely satisfying. What I suggest you do, though, is have a second sandbox installation of the game, and do all your modding and testing there. That way if (when) you bollix it, you can just delete, reinstall, and start again (or better yet use some form of incremental backup), and the version you are using for games and PBEMs remains fully functional.

Regards
Jon