The sender id as it displays on the recipients iMessage is what I would like to reset. However, I cannot find where it is set on the sending device (iPhone 4). It seems to be device dependent as sending iMessages from my iPad 2 displays a different sender name although both devices use the same Appleid.
I hope I understood your question correctly. Try this: go to settings>>messages>>caller id. Choose the email address that is associated with the name you want the recipients to see
I'm pretty sure that it's set in the contact for that person's AppleID/Email Address. Take a look in that persons info in