Piskel is described as 'Remember the good old 2D games and their beautiful sprites? With Piskel you can create your own in a few clicks'. There are more than 25 alternatives to Piskel for a variety of platforms, including Windows, Mac, Linux, Android and iPad. The best alternative is Aseprite, which is both free and Open Source. Other great apps like Piskel are Grafx2 (Free, Open Source), Pixelorama (Free, Open Source), GraphicsGale (Free) and Pixelesque (Free, Open Source).