Newsletter Template Design

We'd like to use somebody to mock up a newsletter for us to send out to an existing database we have. We can provide images, text and the message we want to get across but we'd like someone to put this together into a newsletter for us.

We currently use use an agency that send the newsletter out via Mailchimp to approx 6000 people. However, we'd like to come away from this and have someone advise us how best for us to have the template you put together for us sent out and to this database.