The most eagerly anticipated and potentially most frustrating meetings I attend are by far the unveiling of a new cover. Typically conducted in the Art Directors office I can only hope that he/she has listened to all the "sage" consul and perfected this cover otherwise you'll be telling this emotionally charged art person that their baby is ugly.
To hold your own with the art directors and editors you have to become their primary and trusted source of consumer information. You are the keeper of the newsstand sales data for your titles and for your competition. Numbers take your message out of the realm of personal choice and become irrefutable evidence that the consumer is making the decision of what should be on the covers (not you).
The best way to know what the customer wants is to live with your covers everyday meaning if you have access to a blank wall feature each cover with sales #s right on that wall. You'll be surprised how often your wall becomes a topic of conversation across magazine departments. That give and take is a great learning lesson for all of you.
Without the wall the next best lesson is to periodically spread out 2-3 years of your covers on a long conference table. Include the sales #s on each cover and know the variables associated with each cover i.e. days on sale, page count, seasonality, cover prices, distribution changes and retailer coverage anomalies. If you collect the competition you have an even better analysis to view.
You'll be surprised at what you haven't noticed before. Then after you've done your analysis bring in the art and edit people and walk them through the covers. Tell them why certain issues have greater appeal, what are the key words that made a difference, which images they used actually worked and remind them of the variables that you have been tracking. Stress the key elements of success that you've found. Tell them that they should consider repeating the tried-n-true features again next year - remind them that if it sold well people want it again and again. Ideally, for a monthly, there should be 6-7 tried and true themes repeated and 3-4 out-of-the-box attempts that, hopefully, score with the customers. The rest of the months will be the art directors choices that, hopefully, will be average sellers. This formula 6to7 + 3to4 + 3to2 is a strong plan for keeping sales numbers on par with the prior year while searching for the next best thing.