Nope, you can change every folder icon to a different piece of fruit if you like, but the thumbnails of what's inside won't appear unless it's using the icon inside shel32.dll.
This -- you can easily assign different folder icons, but if you want the live previews, that's technically 2 or 3 different images that get "stacked" together, it's not a single icon. Misunderstood what he was trying to do, sounded like he wanted something a bit automated, hence the desktop.ini file. You can still change it, but you're still limited to one "end" image overall.
ok i get this. can you or anyone else technically explain why this is no problem in linux. i am using kubuntu 14.04 and in dolphin i can set different folder icons and still activate the preview and it will show.
That's just how Explorer works. Microsoft has to target a gazillion people with one program, so they have to pick a balance of usability versus not throwing a ton of options at people. Some people would find Dolphin grossly complex for what they need to do. Say, the difference between Nautilus and Dolphin.. one size doesn't fit all, which is what they have to do, they have to set a baseline of sorts. Doesn't mean you're stuck with it, just like Linux you can replace it with something that works better for you. Even Dolphin. Out of the box defaults doesn't set the OS's capabilities in stone in any way.
Just for example, here's a couple now, Explorer, DOpus, Dolphin, Midnight Commander and Free Commander.. and there's quite a few more. Pick one that does what you want it to do.