You seem to think that sending a pretty card and writing something sweet in it, will make him interested in you. I can't repeat it enough but it won't!
What will happen is that he'll find it so weird that you're getting back to him, clearly trying to get him back (if you make it obvious that that's why you're contacting him, it's game over!), that it will come across as desperate.
Now, forget about all the nice and sweet things you want to tell him (that you mistakenly thought might make him more interested) and tell yourself that this card is only to get in touch with him. Don't send a cute or pretty card: a basic postcard would be a lot better. Keep it really simple, including your e-mail address (Msn address even better maybe?) and mobile and tell him that it would be nice to get back in touch, that you were just wondering how he was doing (for heaven's sake, DO NOT tell him that you've been thinking about him loads recently), and that you'd like to get back in touch.
So I'm assuming you don't have his mobile number?