It's an image I downloaded onto my computer.
When you download or use a image you need to preferably match the pixel resolution your using on your monitor.
Say you have a 1920 x 1200 screen, well you download 1920 x 1200 (or proportionally larger) images, that way you match pixel for pixel your image to your screen, or if the image is proportionally larger (say 2880 x 1800, 150% larger) it scales down (.66666%) to fit perfectly on your screen and doesn't distort.
If you download too small of a image or not enough pixels, like what most webpages have, say 400 x 200, then it stretches and pixelates out and looks ugly to try to fit a 1920 x 1200 pixel display for instance.
If your looking for nice pictures, here's some, just select your monitor pixel resolution (System Preferences > Displays for info)