This maybe a silly question but where are those tag icons you are using in your samples? Can you confirm that they can be added in Tag window by pasting?
Tag abbreviations may be set from the Tags inspector. They’re text, not images. Click the Characters button, and you can use any Unicode symbols on the Character Palette.
Originally Posted by Machster
Folder icons may be set by pasting into the Get Info window in the Finder.
Mac OS X 10.7 adds a large collection of emoji pictures that can be used as tag abbreviations.