Ah, I forgot the terrain/AI stuff was stored in the Editor/Mods folder. Suppose it makes sense that we should just manually make it then so you don't have to explain about making a terrain this tutorial.
For icons, I mean all of them, basically. If you try and preview them in the editor (say, in the sidebar of a character), it gives a "Can't load texture file for preview of icon!" error. If I recall, if the icons were put in the proper location in the mods folder, they'd show up for previewing. Kind of a small thing, but still kind of annoying if you're trying to give a character or item a special icon and you have to refer to the icons by opening the files directly (entailing an extraction of the .pak files.)
