Taking my last post just a little further, for some years now — about thirteen, I think — NASA has been running a website with the Astronomy Picture of the Day. Some years ago, I used to use this site to provide a daily changing desktop picture, and the resource is about as extensive as you can find.
It's still going strong, and interesting to see how the quality of the images, most of them in glorious colour, has improved over the years. Some of them are just spectacular.
Worth a look here.