New item help

[The Rock Worm]

I'm working on an exciting story, but I'm including an item from Penumbra into Amnesia. Now this item can be in your inventory. I already have the object and its texture (as both are visible in the level editor). My problem is this: all items that can be in the inventory has a its own image file, so how do I add its inventory image to Amnesia?

Now I wish to keep the identity of this Penumbra object a secret, so let's call it PO (for Penumbra Object).