The Paths are:
ReplaceableTextures\CommandButtons\BTNCarrionScarabsOn.blp
ReplaceableTextures\CommandButtons\BTNCarrionScarabs.blp
For future reference, if you cant find an icon... look in the WE for the spell its used in and then it will have the path under
Also make sure you have the W3x.mpq selected. To select an MPQ just click the icon that says "MPQ" and browse into your wc3 folder. I should be somewhere in that folder.
~Off topic~ I see you are promoting a map in your sig, If you would like to attract attention to your map/create a fan base, I would suggest posting a thread about your map in the Map Development Section. I would check out some other map posts before posting yours so you can get an idea of how they are formatted.