Besides, I would suggest a special font that might look exactly like a handwritten text (quite big and in italics). It is visually evident that it is not handwritten, but when you asociate the heartly content of the letter with that font you end thinking in the human handwritting.

You could also help that impression if you choose a normal paper context (that is, no dark background with a clear foreground).

Choose photographs with big faces in it and little background.

Use wooden combination of colours that are more more home suggesting themes. At least, colours from the nature!

A nice frame for the photograph also suggest some craftmade thing!

You could even scan the signature!

Enjoy your ilusion!