Yes.
Format your diamond upload file as usual. (Refer to this article on how to upload your diamonds)
Add the column Allowraplinkfeed to your diamond upload file and enter True for the diamonds that you want to display on Instant Inventory only.
You can also add your own diamonds in the Instant Inventory diamond feed but not show them on RapNet. Read this article to learn how to set that up.
Note:
Images: only images uploaded to RapNet display on Instant Inventory
Videos: Click here for a complete list of whitelisted diamond video providers on RapNet