Here's the problem: the icons work in the CS and the in-game inventory, but not in the container inventory. Does anyone know what the heck is going on? If I take the items out of the container, the icons show in my PC's inventory. If I put the items back into the container, the icons go away again.

Think it's related to how most modded items only include icond in the "menus" folder, and not any in "menus50" or "menus80", which are used for other screens depending on resolution of your monitor. Basically, just deal with it. rarely do people make things that lack acceptable descriptions, and since things are seperated by category, you can make some safe assumptions about what something is before picking it up. Think of it as an easy way to determine modded items from non-modded ones.