Recently, I have been using Semi-Retro Skills and I decided to replace the icons of the modified skills with icons that are, I believe, alpha / real early skill icons located at:
guis/textures/pd2/skilltree/icons_enforcer (ghost, mastermind and technician are the same as one listed)
All icons were paired with the skill that seem the best fit; Some were perfect matches, others were a guessing game on my part shrug
Mod goes into "mod_overrides", CONFLICTS WITH ANY MOD THAT OVERRIDES icons_atlas_2.texture
Without the original mod, Icons such as Shotgun Impact and Cat Burglar and others will not appear due to overriding unused icons not seen in base game.
Compression is a little wonky, might go back to it and remake it all in the future / change some icons to further match the original while being faithful to the original icon set.