As in real modification of the client files (old version ... i know ... i'll remove the pic when i get a proper response ) There is no info on client game rules about this so i have to ask ... there is no unfair advantage...
No pw admin will ever say "do what you like"
You can mod anything. As long as you don't use any kind of "bots", it's fine.
there are some mods like hair for barbs that they do let u do depending on the mod u trying to do it is always best to ask a gm first