If default icons just aren't doing it for you anymore, Folder Icon X might be just the tool you need to add your own touch. As the app's name suggests, Folder Icon X is a one-trick (though feature-rich) pony that allows you to add other icons and images to standard folder and file icons to imbue them with a more personal, relevant look. It offers a lot of simple DnD (drag-n-drop) abilities and can import/export a wide variety of formats.
Check out Folder Icon X's product page at Naratt.com for extensive details into the app's abilities. A demo is available, and a license costs $15.00 USD.