The sweaters are usually very bright, loud, and colorful. Many have a 3D affect knit into them (see my second pic). They are usually very abstract and geometric. They are easy to spot in a rack of sweaters.
The show is celebrating 30 years this fall so there are many recent news pieces on the sweaters. Hopefully that will help sell more sweaters! I've got some more Cosby Sweater related links below the pics. Did you ever own or sell a Cosby sweater?
Cosby Sweater Band
100+ News articles on the Cosby Sweater