Some images on Wikipedia/Commons/etc have been uploaded in Gimp's XCF format; as a work format this is pretty good since it supports multiple layers, editable text, various effects etc -- and Gimp is free software, so anyone can download it and edit the source file.
However, we don't currently support in-wiki rendering of the XCF files, so you need to separately upload a flattened PNG or JPEG file.
To save this extra manual step and simplify the workflow, XCF images could be rendered by shelling out to Gimp, or with alternate loaders such as this GdkPixBuf loader: http://blog.reblochon.org/2009/03/gift-to-competition.html
Version: unspecified
Severity: enhancement
URL: http://commons.wikimedia.org/wiki/File:Wikiball.xcf