That is a nice script, but
I usually use the liquid rescale plugin for gimp to resize wallpapers to wide screen aspect ratios.
It doesn't stretch the important features of the wallpaper, and it doesn't crop anything off.
http://liquidrescale.wikidot.com/en:examples#toc1Do you have to compile it?
No,
an older (slower) version it is available in the repositories.
Here is the tutorial if anybody needs any help using the plugin:
http://liquidrescale.wikidot.com/en:tutorial