If you want to save your feelings, I think you should send something with memories. For example, you once said that you would go to Paris together and give him a decoration of the Eiffel Tower, and attached: I'm afraid I won't have a chance to go with you again ... and so on ...)
If you are just friends, don't give anything that will cause misunderstanding, it's just a simple thing, or nothing at all.
But if you are not single, I think it is better not to send this, which will cause unnecessary trouble ... you know ~