Some of the do’s:

Size: Medium to large scale

Shapes: Curvy designs like flowers, fruit, paisleys

Color: Fabrics with 3 or more  colors

Some of the don’ts:

Size: avoid prints that are too small, calicos

Shape: avoid straight lines, geometric lines, strips, plaids, dots

Color: avoid tone-on-tone

The reasoning is that the eye needs to move from one 2″ square to the next.  Your 2″ square should never be small enough to show the entire design because that will stop the eye.  The goal is to have an image that looks like a painting.