I think it would be cool if you can add something like that, I know we already something similar, which is Port. I think the map should be called Blynn's Wrecking Yard. I think it should use custom models to resemble the cars. Also, I think it would be very fun for off-roading because you can crawl over the cars!
There could probably just be a junkyard in a map, instead of having a junkyard dedicated map. Except if you want a huge one...
More precisely, a huge scrap yard they made near Pripiat (I think) to store all the contaminated vehicles. I was too lazy to search a random giant scrap yard in the US, so I went with something I know.
The trouble with a junkyard map is the way that your vehicle would have to interact with it. Every last rusting hulk would be completely indestructible - there's no way that you could possibly damage a rotted-out pigeon in the background, even if you hit it directly with a T-series! If a junkyard does find its way into an official map at some point, I expect it to be filled with either large piles of assorted scrap metal (similar to the small piles of junk currently used in maps like Port), or rusted-out heavy equipment. Of course, there's always the possibility of a European-style junkyard with car racks - just ensure that the cars on the bottom level have all been removed!
