Edit and Save ICO Images with Paint.NET
Paint.NET saves ICO files with a Plug-IN that expands the FileTypes for Paint.NET. You can open, edit and save ICO files with Paint.NET with this addon.
paint.NET addons
Edit Photoshop Files in Paint.NET
You can edit PSD files in Paint.NET with the Paint.NET photoshop plugin that allows Paint.NET to edit or save as photoshop PSD format.