Post Icon plugin??

This might be wishful thinking on my part, but after hours of searching through this sites support threads (only getting catergory icon threads) and google I thought Id give it a shot and ask:

Basically what Im looking for is a plugin that (in my dreams) would have in the post writing area, an upload section where you could upload a thumbnail to represent that particular post, which would be uploaded to a set folder (such as ‘posticons’) and if need be renamed to the post id number eg ’56.jpg’ for easy reference.

Then in the post template there would be a tag for that posts icon such as <?php the_content(); ?> but like <?php the_post_icon(); ?> so on the sites main page the thumbnails would be next to each corresposnding post, or anywhere else where you would like to represent a particular post such as in the sidebar etc

and if there was no uploaded thumbnail for a post it would default to that posts catergory icon in folder ‘catergoryicons’

basically Im looking for a plugin that can do the same as the post icons as these sites, with decent post icon management:
https://www.site73.com/
https://www.xposed.com/

like I said its wishful thinking but I thought It would be a cool thing to have on my site, so I had to check if anybody knew of something that could do this or similar?!