With Photoshop. I open a new document wich is about 100 pixels by 500 pixels and then I choose the pictures I want to include in it and then i'm going to work with it.
I like working n Photoshop π (My education is a Design study so....it shouldn't be too difficult then)
If you like me to make a sig for you, just give me the pictures you want in your sig and I see what i can do π