IbisPaintX is, iPiccy isn’t.
if you are looking for free apps, i would suggest PicMonkey.
but, i highly suggest you save up for a more advanced editing software like Photoshop CS6. it is not only for cover art things, but can be used in other ways. i highly suggest looking at this as it comes with much more features than other softwares and will make editing easier.
I use PicsArt and Ibis Paint X!
With Ibis Paint X I can add contour, eyeshadow, and blush to the characters on the cover. I can also draw on the clothes with Ibis Paint X!
On PicsArt I can make my backgrounds and add the title. I can also make my characters into stickers on it and place them on the backgrounds.
These apps are both free, and I definitely recommend them!
I use Photoshop and Pixlr as well
I make overlays, edit characters and sometimes tries to make a cover with it.