Great wallpapers app on Mac and iOS: Kuvva
Found this great app yesterday for wallpapers: Kuvva. Available on Mac (free) and iOS (1.99$). By the way, I'm in no way affiliated to this company, I just think it's awesome!
Basically it's a wallpaper gallery where artists post their work and the apps grant you access to it. Wallpapers are of great quality and good quantity. On Mac, it can change your wallpaper on a predefined period. On iOS, you can browse the gallery and find new wallpapers.
You can create a free account to store your Favorites and set those as your preferred option for displaying wallpapers on your Mac.