Hello there, the one you can use is pixatopress, there is a free solution and premium one, the other one is plixpress... Otherwise you can get a good theme and using a Gallery plugin... Goodluck
You could use just about any nice WooCommerce theme, and set up your shop with page title "Wallpapers" or "Downloads" and set up wallpaper images as product posts, making each one a free virtual download.
PixatoPress - Free PlixPress ~25 USD or use another one gallery plugin: NextGEN Gallery Lightbox Gallery ReFlex Gallery WP Easy Gallery Lazyest Gallery WP Photo Album Plus OmniGallery Photosmash Galleries Fancy Gallery
I think You should try this Wallpaper theme at binarynote dot come. This theme is specially designed for Wallpaper based website and automatically generate multiple wallpaper for your uploaded image.
If you don't want to pay for premium plugine and theme, so use Wordpress reeoo theme, It is specially designed for wallpaper website. You can check for example Desktop Wallpapers website.
Check below website which loads very fast and have high quality beautiful wallpapers. http://www.wallpapers4k.us