Part of what you ask is already possible! 
They already took the first step with cover images! Click change cover, then click the tab Library and there you find all your uploaded images in Anytype to add as cover! You can even search!
I have no source to link at this moment but I remember them reply-ing on this forum that this feature will be added to other places like you request!
Edit: Well I am not awake haha. The original request is over a year old and I thought and replied as if it was just made haha