open document tab,and image what u want to display,right click on image copy and paste it in <apex:image >

open document tab,and image what u want to display,right click on image copy and paste it in <apex:image >

<messaging:emailTemplate subject="vf template" recipientType="Contact" >   
   <messaging:plainTextEmailBody >
    Congratulations! This is your new Visualforce Email Template. 
    <apex:image url="sahitya0907-dev-ed--c.ap2.content.force.com/servlet/…; /> 
</messaging:plainTextEmailBody> </messaging:emailTemplate>