Quick Any2Ico is a tiny portable free icon creator and converter software that lets you create ICO icon files for your programs, websites, or other purposes and extract images from icon resource ...

You can set a dark or any icon of your choice – but the images have to me in the .ico format. Read: How to change File and Folder Icons. As an example, let us change the icon to a dark one.

Windows 10 makes it easy to make the icons in a folder larger or smaller. First of all, note that changing the icon size of files in a folder changes the size of all the icons in that folder.