This is really unimportant, but I tried it and couldn't figure it out and now it's bugging me.
If I have an image open and hit File > Save as Template... I can create a template that I can see under My Templates when I create a new file. That's all fine and dandy.
However, up at the top is the Default template which I can't figure out how to change. Can someone put me out of my misery and tell me how to change it?