The number of columns is a personal preference but be consistent. A drop-in box with a quote gives the eye a rest. Have only one space after a period. Single spacing after periods makes the appearance flow better. Free legal clipart is available on the Internet.
Glossy paper is more expensive and harder to read because of glossy glare.
Color is always effective. Stay with only two or three. The President's Letter and majority of articles should be in traditional fonts, e.g., Palatino or Times New Roman. Title should be san-serif, e.g., Helvetica. Periodically update your logo and the look of your newsletter.