If you are running RAT on a different machine than your 7D2D server, you will need to manually copy over all of the images from the 7D2D server, to your RAT installation folder in order to see the images for a player's inventory. Please follow the below steps.
In RAT, click Tools -> Export Images
Now, FTP into your 7D2D folder/ItemIcons, copy all of those images into your RAT/ItemIcons folder.
Your inventory images should display now.
In RAT, click Tools -> Export Images
Now, FTP into your 7D2D folder/ItemIcons, copy all of those images into your RAT/ItemIcons folder.
Your inventory images should display now.