Change your Customer welcome email template

It is very simple to do but you have to know the proper process.
If you want to create a customize template for the welcome email then you have to create it first from System -> Transactional Emails , Now add a new Template , create it and save it.
Now go to the System -> Configuration. then Customers -> Customer Configuration ,and then "Customer New account options"
change the Default Welcome Email, Confirmation Link Email, Welcome Email with your template.
save config

Now your welcome mail will send with your template.....