You can make a signature in Photoshop and save it. You open it with your picture and you drag your signature on to the picture. You can sacle it dowwn in edirt transform.
Just click the T in the ps tools. Then set the size and style in the options bar at the topish part of the ps screen. That is if you just want to use one the ps fonts to type your name in with typewriter style.
I have an action for PS that will make you one like I used on this picture. let me know if you want it I can email it to you.
http://www.pbase.com/image/24610457