You can also tack (tie) using a hand embroidery stitch such as a fly stitch or any other that you like (cross stitch, french knots and feather stitch also work well). You can even tack with a small chain stitch flower.
Just run the connecting part (and the knots) in between the layers and you'll have a more 'artistic', less 'rustic' look to the quilt. The choice of fiber used also has a big effect on the overall look...perle cotton or silk buttonhole twist are far more refined looking than yarn or floss.
Tacking doesn't have to look utilitarian or like an after thought. It can be just as beautiful as machine quilting and should never be looked down upon as amateurish.