Six Australian galleries have joined the Google Art Project, which makes museum collections visible in super-high-resolution detail. As well as being a handy way to tour major collections, it's also a potential source of phone wallpaper.
The National Gallery, Museum of Contemporary Art, Art Gallery of New South Wales, National Gallery of Victoria, Australian Rock Art and Museum Victoria have all joined the project. There are hours to be wasted just checking out the collections.
Many of the images would make great wallpaper, but Google has (understandably) designed the pages so you can't easily download high-resolution images. However, you can easily take a screen grab, which potentially gives you an image you can use on your phone. (You could also stitch together multiple images to make a desktop wallpaper.)