How can I add signatures to Preview.app in Lion without using the web cam?
It appears that at present, that isn't an option. When I created a signature file using the FaceTime camera, I see that first of all, there is no unencrypted graphic file created by Preview. Preview did a new key in Keychain titled "Preview signature privacy", suggesting that the signature files go directly from Preview's camera interface to an encrypted file. There isn't a supported way to add a graphic as a signature, and the encryption makes it difficult to bypass the approved new signature process.