just follow that guide line and write what you want it to be like etc. etc. then once you done that ill give it ago, got loads of time freeLink to the picture/render you want to be used.
A size of the signature : (150x350px,120x330px etc)
Theme/style : (if you know what kind it is preferable,if you dont,it will be up to the desgner)
Text & other deatils :