I tried following the steps found on the CK2 Workshop Page, i.e. :

From
GAME_HOME = os.path.join(PROGRAM_BASE, "Steam/steamapps/common", GAME)
To
GAME_HOME = os.path.join(MOD_HOME, "biggerinterface")

From
SCALE_UI_PREFIX = "scale_ui_%sp" % res_height
To
SCALE_UI_PREFIX = "biggerinterface_%sp" % res_height

From
scaled_dir = os.path.join(CWD, "%sp" % res_height)
To
scaled_dir = ""

The script start fine, however it always stop with the last line in the log :
INFO:rescale_gfx.py:Load dds file = achievement_we_bled_for_this.dds

I tried multiple different mods, none had a gfx/interface/achievements folder in them (why would they? a mod can't use the base game achivements)

I tried seeing from where the script went to search for the achivements folder but ended up with nothing, is there another edit that would be needed to use the script on another mod folder?