This mod from Autologic changes the player icon from Marked One to Strelock. That's it.
-- New Strelok Icons for Marked One - S.T.A.L.K.E.R. - Shadow of Chernobyl -- May 6, 2009
If this is the first mod you are using, open fsgame.ltx in notepad and at the gamedata line change both variables to true (one of them is already true).
Look at Previews.jpg and find which icon you want. Go into the folder with the name of that icon, then extract the gamedata folder to your S.T.A.L.K.E.R. - Shadow of Chernobyl game directory and overwrite all files.
This is just a small icon pack that turns Marked One's icon into a picture of Strelok from the game. It may spoil some of the story for you if you haven't beat the game. These icons are compatible with OL2.2 or OL2.2 + Arsenal Merge.
FYI, ss_a_05-06-09_17-24-31_(l07_military).jpg is of Strelok_4.