Yes, the pack art DOES influence sales. Also, it influences what cards you receive when buying booster packs.
For example, long ago, I bought 2 Scrafty packs and 2 Excadrill packs from Dark Explorers, I pulled 2 Holo Volcaronas, Holo Blissey, and Holo Haxorus. All holos pulled in all 4 packs...