Lo más fácil es maquetando con HTML pero si, hay una forma: embebiendo imágenes al e-mail. Un ejemplo con CDONTS:
Código:
Set objMail = Server.CreateObject("CDONTS.NewMail")
objMail.Importance = 1
objMail.From = request("strName") & "<" & request("strEmail") & ">"
objMail.To = request("strTo")
objMail.Subject = "Example of HTML EMail with Embeded Image"
' this is my messages HTML
strMsg = "" & _
"<html><body bgcolor=red>" & _
"<a href=""http://www.RealWorldASP.com/""><img src=""logo.gif"" border=0 alt=""RealWorldASP"">" & _
"</a><p><font face=verdana>Example of a HTML Email with embedded Image<P><br>" & _
request("message") & _
"</body></html>"
' set the format of the email to html, etc
objMail.BodyFormat = 0
objMail.MailFormat = 0
objMail.Body = strMsg
' attach our image file and set the url to simply logo.gif
objMail.AttachURL server.MapPath("logo.gif"), "logo.gif"
objMail.Send
' destroy the email object
Set objMail = Nothing
ASPMail tambien ofrece esta posibilidad:
http://www.aspemail.com/manual_04.html
Un saludo