Don't put up with boring folder icons ...
Get Info (⌘I) for folder, icon at top left.
Get Info (⌘I) for folder icon you want to copy, icon at top left.
Click on icon you want to copy, copy (⌘C), click on original folder icon, paste (⌘V) ... Voila !
This also works extremely well for folder contents, especially ones containing photo's
Select favourite photo in folder, copy, and paste into folder icon as above.
Basic examples:
The same technique works for many icon images off the web.