ok well u can use a button..there is no code for a sig but if u want to connect it then yea
1) pick out your pic u want to link to your website..i duno if there is a certain size to use since im new but yea
2) host your pic
3) fill out this code :
4)put it in ur sig
5)click update my signature
6)ur done!!
well hopefully that helped..

EDIT//
i suggest
imageshack to host ur pic but if u already have one then..yea