Actually in contacts.apk in \res\drawable-hdpi-finger, ic_contact_list_picture. I also replace ic_contact_picture, ic_contact_picture2 & ic_contact_picture3 which I believe are used for home screen shortcuts.
There are ic_contact_picture, ic_contact_picture2 & ic_contact_picture3 in framework-res.apk in \res\drawable-hdpi but I think the one in contacts.apk are the one(s) to replace.
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