The SXGA Wallpaper size (1280×1024px)
1280x1024 pixels is SXGA, an unusual 5:4 resolution that was the standard for classic 17-inch and 19-inch LCD monitors. Its nearly square shape is noticeably taller and boxier than modern widescreen formats, which is why a 16:9 wallpaper looks so wrong on these displays, either heavily letterboxed or stretched until circles turn into ovals.
Resizing to a native 1280x1024 respects that 5:4 shape and fills an SXGA screen properly. These monitors are still common in offices, point-of-sale systems, industrial setups, and among retro-computing enthusiasts, so a correctly proportioned wallpaper keeps everything looking natural without the distortion that ruins photos and faces when the aspect ratio is forced.
Compositionally, the taller 5:4 frame favors subjects that are more vertical or centered than a widescreen scene; sweeping horizontal panoramas will feel cramped here. There is no benefit to a huge source since the panel tops out at 1024 vertical lines, so resizing to this exact size is ideal. Keep the focal point centered and away from the taskbar. This tool resizes entirely in your browser, so your image is never uploaded, it is free, and your original quality is preserved while the file is fit to the boxy 5:4 shape SXGA monitors expect. Verify your screen resolution, as older panels vary.