Looking through my Developer/Applications/Utilities folder on my Mac, I was surprised at the shockingly bad icon for the USB Prober app. It is clear from the 512 pixel version that the "icon" is simply a photo of a USB connector. I made a replacement icon, that could also be used in other contexts.
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:origin()/pre00/9c96/th/pre/i/2010/248/4/9/onceagain_by_delacro-d2y1wt5.png)
:origin()/pre00/f5ff/th/pre/i/2010/205/7/e/squaredly_mac_by_willyork.png)
:origin()/pre00/a407/th/pre/i/2011/057/c/c/windows_7_tray_icons_by_kaamzzo-d3a62sg.png){kind=icon}
:origin()/pre00/2434/th/pre/i/2009/187/6/7/google_talk_icon__pngs__psd_by_hydrattz.png){kind=icon}
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:origin()/pre00/4cf8/th/pre/i/2010/003/9/b/hel__by_kyo_tux.jpg)
:origin()/pre00/5bc1/th/pre/i/2010/081/7/5/apple_icons_by_melissareneepohl.jpg){kind=icon}
:origin()/pre00/d68a/th/pre/i/2010/097/4/6/apple_profiler_by_matanarie.jpg)
:origin()/pre00/de43/th/pre/i/2008/324/4/0/green_and_blue_by_wilsoninc.jpg)
:origin()/pre00/2f34/th/pre/i/2007/335/0/e/stacks_by_nemone.jpg)
:origin()/pre00/b710/th/pre/i/2010/225/e/e/compass_by_shlyapnikova.png)
:origin()/pre00/40fb/th/pre/f/2014/303/9/b/evernote_icon_by_tinylab-d41mjgw.png){kind=icon}
:origin()/pre00/1261/th/pre/i/2010/199/0/0/safari_icons_by_soundforge.png){kind=icon}
:origin()/pre00/6583/th/pre/i/2010/216/3/1/mac_mini_server_by_b3l4m4n.jpg)
:origin()/pre00/6cc3/th/pre/i/2010/199/2/4/usb_prober_by_nealyoung.png)
XCode's icons are not that great i concur. Your's looking good with just a little curve missing on the cable's base.
Thanks!