Have you ever wondered why YouTube contains every video in the world that you could think of? The reason, of course, is the fact that users do the all the work of curating and uploading.
Desktoppr is a website that, similarly, lets users upload and freely share hi-res wallpaper images.
It connects with your Dropbox folder to make downloading (and uploading) wallpaper images a simple, seamless affair, and to provide a convenient folder that can be used for wallpaper shuffling.
Note that Desktoppr is still in beta, is still being developed, and at the time of this writing you will have to request an invite to join.
How to use: once you have registered and linked Desktoppr to your Dropbox account, you will be able to use a little icon on the bottom right of each image that will automatically sync it to your Dropbox (see screenshot to the right), which makes grabbing wallpaper images and exceedingly easy and simple affair.
Social functions: you can follow other users and be followed, and you can upload your own images by moving them to your Dropbox folders.
Note that Desktoppr requires that you hold the copyright of an image that you upload (or, I expect, that an image be in the public domain); although, to be honest, looking at the images on offer it seems to me that that is unlikely to actually be the case. They also require a minimum size of 1280×800, and that the images be “work friendly” (tasteful nudity seems to be OK, although it is filtered out by default).
The verdict: a wonderful source for curated, wonderful images. Desktoppr aims to create a community around wallpaper images, and the Dropbox integration makes participating in the community easy and convenient.
One thing Desktoppr needs is a search box, and maybe a system of tagging images by topic, etc.
Check out Desktoppr (you may need to request an invite; I got mine about a week).