Solved this by creating my own WorkflowType, givit it the same Settings as a the "Send email" WorkflowType, but then i could make my own Workflow Execution. Then i was able to add a html structure surrounding the "Message" setting and include my footer and custom css.

Post´s code in case somone runs in to the same scenario:

CustomWorkflow.cs

public class CustomWorkflow : Umbraco.Forms.Core.WorkflowType
{
    public CustomWorkflow()
    {
        this.Name = "Send email with custom stylesheet and html structure.";
        this.Id = new Guid("91517EB2-8D61-483C-A3DA-7850FCE05123");
        this.Description = "Sends a email with a custom stylesheet and html structure.";
    }

    [Umbraco.Forms.Core.Attributes.Setting("Email", description = "Enter the receiver email", view = "TextField")]
    public string Email { get; set; }

    [Umbraco.Forms.Core.Attributes.Setting("SenderEmail", 
        description = "Enter the sender email (if blank it will use the settings from /config/umbracosettings.config)",view = "TextField")]
    public string SenderEmail { get; set; }

    [Umbraco.Forms.Core.Attributes.Setting("Subject", description = "Enter the subject", view = "TextField")]
    public string Subject { get; set; }

    [Umbraco.Forms.Core.Attributes.Setting("Message", description = "Enter the intro message", view = "TextArea")]
    public string Message { get; set; }

    public override WorkflowExecutionStatus Execute(Record record, RecordEventArgs e)
    {
        if (string.IsNullOrEmpty(this.SenderEmail))
        {
            // Gets the Notification EmailAddress from the umbracosettings.config file.
            this.SenderEmail = UmbracoConfig.For.UmbracoSettings().Content.NotificationEmailAddress;
        }

        if (record.RecordFields != null && record.RecordFields.Values.Any())
        {
            // To send Email to the visitor, enter {alias} and get field value from the form.
            if (this.Email.ToLower().Contains("{") && record.RecordFields.Values.Any(p => p.Alias == (this.Email.ToLower().TrimStart('{').TrimEnd('}'))))
                this.Email = record.RecordFields.Values.First(p => p.Alias == (this.Email.ToLower().TrimStart('{').TrimEnd('}'))).ValuesAsString();

            this.Message += "<p>";
            foreach (var recordField in record.RecordFields.Values)
            {
                this.Message += "<strong>" + recordField.Field.Caption + ":</strong>&nbsp;<span>" + recordField.ValuesAsString() + "</span><br/>";
            }
            this.Message += "</p>";
        }

        var mailhandler = new MailHandler();
        mailhandler.SendEmail(this.SenderEmail, this.Email, this.Subject, this.Message, null);

        return WorkflowExecutionStatus.Completed;
    }

    public override List<Exception> ValidateSettings()
    {
        var exceptions = new List<Exception>();

        if (string.IsNullOrEmpty(this.Email))
            exceptions.Add(new Exception("Please enter Email!"));

        if (string.IsNullOrEmpty(this.Subject))
            exceptions.Add(new Exception("Please enter Subject!"));

        return exceptions; 
    }
}

MailHandler.cs

public class MailHandler
{
    public bool SendEmail(string from, string to, string subject, string message, List<Attachment> attachments)
    {
        try
        {
            var av = EmailTemplateConverter.GetMailTemplateWithLogo(message);

            using (var client = new SmtpClient())
            {
                using (var msg = new MailMessage(from, to, subject, message)
                {
                    IsBodyHtml = true,
                    BodyEncoding = Encoding.GetEncoding(1252),
                    Sender = new MailAddress(from, to)

                })
                {
                    if (attachments != null)
                        attachments.ForEach(p => msg.Attachments.Add(p));

                    msg.AlternateViews.Add(av);

                    client.Send(msg);
                    return true;
                }
            }
        }
        catch (Exception)
        {
            return false;
        }
    }
}

I didnt manage to post the EmailTemplateConverter class in this post, but its pretty standard. Google it or i can send it to whoever is interested.