I think both Aseprite and Graphics Gale are great tools for pixel art. If you have Aseprite on Steam, you can try the experimental branches to try features before they are fully fledged. I've been using the tile branch and playing with it for some time now.

You can also compile for yourself if you want - even though I have bought it on Steam I have my own build too that I use in an old Linux computer when I want to draw in non-distracted almost offline way.