Questions on modding the terrain and npc graphs

[wuxiangjinxing]

I attempted working on the Oldrpg addon in order to allow it work in 1.5.5. One simple method I tried was simply changing the folder "oldrpg" to "shockbolt" so that I hoped it would overrite the original graphs. However, only the player's graphs are modified in the game by doing this, while the terrain, monsters and npcs still kept their original appearances.

I got very confused because theoretically speaking those files should be overritten since the new graphs are in the "override" folder, and those new ones work just fine in the original "oldrpg" folder. Does any of you understand what happened or what mistake did I make? Thanks a lot.