Paint these on the t-shirt, along with some romantic graphics like a heart or a boy and a girl kissing. Send this to your gal and believe me, she will be thrilled to see the efforts you took in making the gift yourself!
Communicate your true feelings for her through these letters. Tell her how you spend your day, people that you meet and most of all, how much you miss her! These letters will make her feel that she is near you and is a part of your new environment. It will definitely enhance the connection between you two!