If you have a galaxy note you should be able to create something in s-note and attach it as a media file to send (like a text)
Or you could go low tech...write out your message (pen paper) take a photo of it...send the photo
You would need an app to create the card. Something that allows you to draw. Your best bet is probably a paint/image app. Many of those allow for freehand drawing.
You would then have to save it as an image on the phone, and add the image to the texts you wish to send.
I can't say what app would work for you, in the case of creating the image, but if you do a search on Google Play you should be able to find many free apps that can help you create freehand drawn images.
Now if you are wanting to just change your text messaging to use handwriting, I don't know that this is possible, at least without, again, an app. And this would also not send the text via your phones messaging, but through what ever app is allowing you to make the message.
In the end I would say the image creation/add to text message option would be your best bet.