I'm wallpaper-obsessed and I recommend Kuvva (http://www.kuvva.com ). It gives you curates bursts of 7+ quality original wallpapers every week, on iOS and OSX, thanks to a partnership with actual art galleries.
This said, I think there's still a niche for a website or app specialising in new minimalistic wallpapers. Also, I'd pay for a "wallpaper-on-demand" service where one could order custom pics - I think photo websites like 500px are missing a trick there.
4walled.cc is a similar if much less polished service. Also see WallHaven.cc, which some of Wallbase's staff is working to make Wallbase's new home.
[1] http://www.reddit.com/r/YouShouldKnow/comments/1tbux9/ysk_ab...