How to universally change all instances of an icon and other questions

This is a multi-part question (I've done quite a lot of search-engine research with no conclusive results):

As seen in the linked-to image: I've created a custom folder icon (A purple folder) and embedded it in a self-made .dll file using Resource Hacker:

http://www.angusj.com/resourcehacker/

I set that folder-image as the icon by selecting Properties > Customize > Change Icon in the right-click menu of the folder named GameXN Figure 1..

However, as you can see, the image shown in Figure 2. is the only image that has changed. Normally that would be the icon shown in Figure 3..

Is there a way to cause windows to replace the actual desktop icon (The Yellow Folder with the white files contained within it - called GameXN Figure 1.)?

Is there a further way to cause Windows to interpolate the yellow folder as the purple folder, thereby allowing it to dynamically preview the contents of the folder (In the case of Figure 1. the white sheets of paper)?

And finally, where can I locate the image of the tiny Yellow Folder Figure 3. to edit that icon so that it's purple?

Also, when highlighting a file (Single-clicking on it) what do I need to change to ensure that highlighted folders appear in the new purple icon colour rather than appearing as yellow when highlighted?

(I'm aware there are custom icon sets online to download but would prefer to do this myself as it's a learning process.)

@Thelps
I'll attempt to address some of your issues:

- the tiny folder image (figure 3.) is not an Explorer icon per se, it's a shortcut to create a new folder, part of the Quick Access Toolbar, which can be removed:



- the self made .dll you created is probably going to pertain only to the folder you created it for. If you want the custom icon to represent all Explorer Folder images, you'll need to replace 24 items:



in imageres.dll/Icon/9 thru 40

Thanks for the reply Edwin. :)

Do you know what needs to be done to cause the folder in Figure 1 to appear as a purple folder but still show the interpolated custom file thumbnails (the white sheets that preview a random selection of files contained within the folder)?

Are there specific dimensions that a folder icon needs to meet to cause windows to do the above? For instance, I can't create the image of, say, a taco, and have windows still preview the folder's contents within the icon? Or is this possible?

From what I can tell, the custom .DLL file only pertains to folders where I specify that .DLL via Properties > Customise > Change Icon​.

Your assistance is greatly appreciated!