Hello,
We were really happy to see the new feature released yesterday for setting custom permissions on Media Library collections:
One thing that would make it even more useful for us would be the ability to restrict an Image field so it can only use assets from specific collection(s).
For example, we could create an “Icons” collection that is managed only by admins. Then for a specific Image field, we’d want editors to only be able to pick assets from that “Icons” collection. That would help prevent people from uploading or selecting assets from elsewhere in the Media Library by mistake.
For us, this would be a really helpful way to keep things more consistent and avoid editors using the wrong assets.
Curious to hear what you think, and if anyone else has the same need, please upvote this request 
Thank you,
Nicolas