Hanger appeal refers to the attractiveness of a garment when viewed on a hanger (rather than being worn). A garment has hanger appeal if it looks good "on the rack" and would entice someone to look more closely, and perhaps try it on and buy it.

“衣架魅力”指一件衣服挂在衣架上（而不是穿在身上）时候展现出来的吸引力。一件衣服如果有“衣架魅力”，就会吸引人们走近细看，可能还会试穿，然后买回家。

For example:

Girl, these tops don't have hanger appeal. They don't look good 'til you put them on.

姑娘，这些上衣挂在那里没觉得好看。你穿在身上以后才觉出好看来。