The cosmetic business model has seemed to work well for Valve. Team Fortress 2, CS:GO and Dota 2 use this model, from which Dota gathered worth of $600'000 only from donations towards the game's yearly championship. The players received some in-game items from the donation, which gave them cosmetic items for playable characters and new UI skins. I personally like the idea, as the highly competetive games stay balanced as the cosmetic items do not give any edge to their owner.

Valve also gives the cosmetic items as random drops after matches or from spectating competetive games. The players are then able to sell these items to other players trough Valve's market. From the trades Valve takes a procentual fee (or margin, that is), which can raise quite high as some knives in CS cost over $300 and some couriers in Dota have been sold as high as $9000 a pop.

Even though the cosmetic business model sounds like a golden road, I've yet to across any mobile game which would have used it.