For some reason, most people's icons are way too big on the dock. I really like the icons from icreatemagazine, but the icons are enormous compared to the actuall OSX icons. The best example I've seen is this person's work, although I don't like them as much as some others, these have been made to fit well on the dock.
Image
Image
http://dribbble.com/tristanedwards
Edit: Hmm, I just noticed that there are a few that are exactly the same as the OP's. Well this is awkward.
Haha. I was thinking the same thing. lol. I'll snag a few from here too anyway.
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I see, thanks. What about if I want to go back to the default ones? Do I need to make backups or will OS X take care of that?
That I'm not 100% sure about. Sometimes if I try to change the icon again, it reverts to the original. So I'm pretty sure the original icons are still there, so there could be some terminal command or something to change them all back. If you want, there is the third party app called candybar that can revert them all back to the original.