Valve has solved this by crowd-sourcing cosmetic items through the community. In Team Fortress 2 (which uses the same kind of skin/item system as Dota 2 and Counter-Strike: Global Offensive) 90% of the items have come from the community, who then also get to share in the profits [1].
[1]: http://www.theverge.com/gaming/2014/1/16/5316248/on-average-...