XGimp is described as 'adaptation for iPhone and iPad of the app GIMP (GNU Image Manipulation), which freely distributed program for tasks as photo retouching, image composition and image' and is a Image Editor in the Photos & Graphics category. There are more than 100 alternatives to XGimp for a variety of platforms, including Windows, Mac, Online / Web-based, Linux and Android. The best alternative is GIMP, which is both free and Open Source. Other great apps like XGimp are Krita (Free, Open Source), Adobe Photoshop (Paid), Paint.NET (Free Personal) and Affinity Photo (Paid).
Krita is a professional Free and open source (FOSS) painting program. It is made by artists that want to see affordable art tools for everyone withith concept art, texture and matte painters, illustrations and comics.
darktable is a virtual lighttable and darkroom for photographers: it manages your digital negatives in a database and lets you view them through a zoomable lighttable. it also enables you to develop raw images and enhance them.
MyPaint is a fast painting program with an emphasis on full-screen use. It lets you focus on the art instead of the program. You work on your canvas with minimum distractions, bringing up the interface only when you need it.
Pixlr® makes it easy to transform everyday images into stunning works of art. Whether you’re applying a quick fix to your photos or adding your personal touch with effects, overlays, or borders, Pixlr has everything you need to make your moments beautiful.
Pixelmator is a powerful, beautiful, and easy to use image editor. Featuring an elegant and streamlined single-window interface, it puts all the focus on the images you edit, rather than what's around them.