Very easy
Do you mean you want their name to display when you ipad imessages your iphone?
2 ways to do it
You can either add another contact and call it iPad Message for instance and just add your iMessage email in there.
Or
If its another persons phone they simply need to add the same email address into your contact on their phone.
I dont think its possible to not display your email address mind you if you are not already added at all in their contacts, i.e if you're imessaging an aquantaince and not a close friend via iMessage.
iMessage i designed for more personal use between friends and family unless you dont mind sharing your email address.
Why not just add another email address in iMessage to use if you're worried?