One thing I love about Verve is you can save a PNG file then open it again in the program. It becomes no longer just a static image but liquid paint
So you can paint on the image again and the image reacts to the brush! It's like resuming working on a oil painting that is still wet. I get some of my best ideas this way. I can just play with the image and if I screw it up no problem just open it again. I am not aware of any other 2d paint program that can do that!