If Valve has done one thing very well with it's Steam platform games, it was finding ways to bring players into the creative process and ride the coat-tails of their ingenuity into wealth. For a few years now Team Fortress 2 and DotA 2 players have been able to create items for those games, submit them to the workshop, and potentially get approval from Valve. If they got approval they could even get money every time another player purchased that item. For a game company it's basically printing money; you earn goodwill with your fans by letting them contribute and giving them a cut, and you get art assets for your game without having to hire as many artists. Plus the community will tell you which ones they want.