For a perfectly square table you may be tempted to use four matching pieces for a perfectly symmetrical look. However you can get a more intriguing look by using two pieces or groups one in each corner. Try a tall vase or lantern in one corner with a stack of two or three books in the other (and an airy sculptural accent on top).
Another consideration is how it will sit on your floor or rug and if it will damage those surfaces. Splintered table legs or rusty metal bases can scratch or stain the flooring. Secondhand stores sometimes leave those areas unrefinished so be sure to check. Sculptural wood coffee tables tell their own story and can add a natural element and warmth to a room with multiple upholstered pieces. Sealers and of course coasters can help protect the surface from water damage.