When the player is carrying an object, this property determines how it appears is their inventory.
Default will show the object itself, and it will be rotating. The majority of objects have this setting, such as the sword, scrolls, keys etc.
Alternate Model will show the any model from obj (either the .crf or the folder). Useful if in game the object had moving joints. With Default those joints might not be shown property. Using Alternate Model an un-jointed model could be referred to instead.
Alternate Bitmap will show an image. This is used for carrying bodies. E.g. cswgard1 refers to obj\cswgard1.pcx - a picture of Garrett carrying a guard.
Property Name: InvRendType