Please see the attached sample picture, for more detail. (The screenshot shows my personal game configuration, which has elements that this mod will not change. This mod will neither change your countries' unit colors, nor install the roundel unit-country-identifying symbols.) The sample has infantry, artillery, garrisons, a small garrison, an armored train, and a fighter plane squadron. I've changed the symbol for small garrison (it is now a smaller version of the garrison's plain rectangle, in the shape of a simple stockade, following the traditional method of deriving such symbols). The only other significant change is making armor more of a caterpillar-track shape, to match the traditional armor symbol, as opposed to the game's default oval shape.


Here is the file, hosted at Zippyshare. It's about 0.35MB (one-third of one MB) in size.
Comments, questions, and suggestions welcome.
These unit counter graphics are .png files which go into your Commander: The Great War directory, into the folder \data\graphics\units and please back up your original files before you install these. To back up your files, copy-and-paste (to a new, separate location) the corresponding files from the \data\graphics\units folder (or, simply back up the whole units folder, by copy-and-pasting a copy to a new location, it's about 27MB in size).
[Current NATO Joint Symbology (APP-6(C)) endorses the square frames for some uses (notably for neutral elements), but the U.S. Department of Defense Standard (2525C) universally endorses the familiar rectangle shape, which my own eyes prefer.]
As of 07 October 2016 I've uploaded a second version of these unit files. The changes are to the Armour and Armoured Train units, which I thought were not up to par.