SkySketch can save/export images as .png files.
Currently, SkySketch is based on the equirectangular panorama layout. Additionally, files can be exported as cubemaps for use in other applications - but you should always keep your work saved as an equirect (that's the default layout used by the save commands) as well, if you still plan to edit it in SkySketch.
[TODO: Picture comparing panorama unwrap layouts]
The following image types can currently be imported either onto the canvas or as brushes: .png, .jpg, .tga - this goes for panoramic pictures to paint on, as well as the brushtips that you can use to paint.
Support for additional formats and panorama layouts, including layer support, is planned for the near future.
To import brushes,