Since I didn't receive any replies, I assumed there isn't really any "Library" as such, or doesnt have this functionality. I remember seeing one on WC3C or on Jass Vault but have yet to find it.
So I started one that does what I want on WoWWiki.
http://www.wowwiki.com/WC3_Icons/Map_editor_icon_library .
Feel free to add to it, but please stick with the styles and fields already in place.
No Doubt. I can't believe we can't pull the data out of the mpq's. It's in there somewhere!
Just an update.
This database/icon library is coming along nicely. Check it out. Contribute if you have time and the necessary skills and patience.
http://www.wowwiki.com/WC3_Icons/Map_editor_icon_library