Some of our customers prefer to design their own cover.  We are fine with that.  Please contact us so we can send you a design template to make your work easier.  We can accept files of nearly any type.  Vector graphics (ai, eps) do not have issues with quality loss if they are enlarged.  Bitmap images (jpeg, tiff, gif, png) are prone to quality loss if they are enlarged too much.  If you prefer to use a bitmap image please make sure it is a high resolution file.  Feel free to contact our design department (844) 526-6228 for further help and instructions on where to send your design.