Resize any image on novalis.org. Just paste the URL below and enter a size. These are maximum dimensions -- that is, the image will be sized such that it can fit in a box of the selected size while maintaining the same ratio of height to width. If you select "letterbox", the generated image will be exactly the dimensions you select, with black filling any unused portions. Images will never be made larger.
If you want to use this as a desktop background, use the image below to find your screen size: