If you can use apps on your phone, you need to get the Backgrounds App.
It rocks. They have the best backgrounds anywhere and they're all super high quality and they're all FREE.
Plus, there is a Flickr pool for the Backgrounds App where you can submit your own photos to appear on the Backgrounds App so people can use your pictures on their phones!
When you do an app search, you'll recognize the Backgrounds App by their graphic, which looks like this:
So start submitting your awesomest pictures, please (especially mushrooms and/or sparkly stuff). I want to use them on my phone. Thanks.