Never repeat icons. No two issues should contain the same icons, though icons often do end up looking alike. Aspect ratio change in icons is acceptable, but not excessively. Also, always save icons as bitmap files when saving them in Photoshop. It saves hard disk space, and causes less hassle.
Horizontal icons follow all the rules of normal icons, but are more than one column in length.
They should never be used to break up text. Instead, they should be placed in between articles in place of horizontal lines, or at the bottom of articles to take up space left on the page. Like normal icons, they should be no taller than an inch and should fill their box. This is doubly important for horizontal icons, however, as they draw more attention than their normal counterparts. We saved the most difficult part for last.