monitor resolutions with aspect ratio 4:3
640x480
800x600
1024x768
1152x864
1280x960
1400x1050
1600x1200
2048x1536
3200x2400
4000x3000
6400x4800
widescreen monitor resolutions with aspect ratio 16:9
852x480
1280x720
1365x768
1600x900
1920x1080
widescreen monitor resolutions with aspect ratio 16:10
1440x900
1680x1050
1920x1200
2560x1600
3840x2400
7680x4800
Although 16:9 seems to be the new standard since a couple of years (especially for movies and games) both 4:3 and 16:10 are still widespread. According to a source on wikipedia they each are used by about 25% of all users, with the remaining 25% sharing all other aspect ratio's.
The earlier wallpapers came in two sizes:
4:3 - 1152 x 864 and
5:4 - 1280 x 1024
The more recent wallpapers come in three larger sizes:
4:3 - 1600 x 1200
16:9 - 1600 x 900
16:10 - 1680 x 1050
If and when images are available in larger sizes, wallpapers may be available in corresponding larger sizes.
Using wallpapers with a different aspect ratio than your monitor may cause distortions. Make sure you adjust your settings to prevent this. The letterbox effect is in most cases preferable over a distorted image.
Downscaling (using a wallpaper with a larger size [1680x1050] on a monitor with a smaller resolution [1280x800]) should be no problem as long as you stay within your aspect ratio.
Upscaling (using a wallpaper with a smaller size [1280x800] on a monitor with a larger resolution [1680x1050) might be ok in some cases, depending on the quality of the image. A lot of the images will however not generate a satisfying result. Make sure you adjust your settings to prevent this.
