I found a bunch of my little pony filly icons for the mac interface, but they were all uploaded to megaupload *sigh (>_>)
Anyway, I took the png file of google and converted them to icons. I don't take credit for drawing them, just converting and reuploading them.
To customize icons, download these. put the folder anywhere you want. right click on the thing you wanna customize. It'll either say customize at the bottom or the top. you can do the rest from there. =/
Edit: Went back and fixed Luna, Gummie, and Colgate.
Edit: Made a v2: [link]