Here's how it works:
Fn shows up as Subtype
Data1 is Fn ID
Data0 is the icon that shows up in the inventory
Data2 is the icon that shows up on the object itself
The custom texture option is to select the custom icon set image that shows up on the object itself. The custom icon set that shows up in the inventory corresponds to the icon set selected on the level/dialog select screen. I have the Wop texture defaulted to the standard icons that came with the Editor.
I suggest you keep the icon set image the same for both the inventory texture and the object texture unless you like mismatching images for some reason. Same for Data0 and Data2 as well.
Now, the subtype (Fn) acts a little strange. Positive numbers correspond to left-clicking the Fn option in the original Custom Item wop, however for using gloves, spy-eye, etc you need to start counting negatives by right-clicking through the Fn option.
Example: Win Adventure is 1, ID On Local is 2, Gloves is -1, Lamp is -2, GlowGem is -3, and so on. I have only tested the Gloves and Win Adventure, so please correct me if I'm wrong.
I think it acts this way because if you start right clicking from None, you will eventually see "Map Piece" and "Glyph". Because these functions are not supported in the editor at the moment, Patrick made it so that it will skip these when left-clicking through the functions.
