I am currently using a new pixel program called "pickle" it doesn't have onionskinning, but it does have copy/paste, unlimited undos, and you can create your own custom hexcode palettes to save for later use, with only the colors you need at the time. plus you can do animated or terrain tiles, it saves in jpg, gif or png format, as well as its own format(to re-edit later). actually pretty simple and easy to figure out, and the cost? only $9 USD. (FYI, not a promo/plug, i just think it's worth trying out)