Many screen resolutions are proportional in a 4:3 ratio,
so an image scaled to fit in a different-sized screen
will still be the correct shape, although that scaling
may impact quality. Common wallpaper resolutions are connected
to common desktop resolutions: 800x600, 1024x768, 1280x1024
Users with widescreen (16:9 or 16:10) monitors have
different aspect ratio requirements for wallpaper, although
images designed for standard (4:3) monitors can often
be scaled or cropped to the correct shape without undue
loss of quality.
Wallpapers are sometimes available in double-width
versions (e.g. 2560?1024) for displaying on multi-monitor
computers, where the image appears to fill two monitors.