Issues:
Looking at a natura crop throws http://pastebin.com/ALCa2NLC
Farmland shows up as dirt. (Could add if its wet or not)
Ideas:
Redstone information. (Power level, Repeater state, On/Off, Enabled/Disabled ETC)
Crop growth level.
Display block attributes (Shearable, farmable,ETC) the same way as mobs display armor/weapons.
Burnable block attribute. (Like wood)