So I just learned we can customize the graphics! Awesome!

... But how do we get it from the Steam workshop on GOG?

Found out myself how to get graphics mods from the Steam workshop:

https://steamworkshopdownloader.io

Just use that and SteamCMD to download the files then copy them to the gfx directory in the installation folder.

Thank you for the information - a shame that the graphics mods aren't available via GOG though.

As steam has killed the downloaders this is now the only working one I know of,
from this thread
https://steamcommunity.com/workshop/discussions/18446744073709551615/2333276539614268688/?appid=576770&ctp=1

https://www.dropbox.com/s/0fasl6rrss8c0av/tex_music_modv5.zip?dl=0

no worries, it is just simple grafics and tons of songs
but it does overwrite the cool original title screen

wrote a simple batch to keep switching it with the new one,
just rename the old title screen

c:\GOG Games\Low Magic Age\gfx\bgs\main_menu.jpg into
main_menu_1.jpg
before unpacking the zip

then create a txt file in the game directory and copy this

@echo off
set gamedir = "c:\GOG Games\Low Magic Age\"
if exist "%gamedir%gfx\bgs\main_menu_1.jpg" goto 2
ren "%gamedir%gfx\bgs\main_menu.jpg" main_menu_1.jpg
ren "%gamedir%gfx\bgs\main_menu_2.jpg" main_menu.jpg
goto 3
:2
ren "%gamedir%gfx\bgs\main_menu.jpg" main_menu_2.jpg
ren "%gamedir%gfx\bgs\main_menu_1.jpg" main_menu.jpg
:3
start "Launch Low Magic Age" "%gamedir%Launch Low Magic Age"

save as LMA.bat
and keep launching the game with it instead