Pro Motion's price has dropped fairly recently, well worth it.

I stumbled across another open source DPaint-alike not too long ago: EvilPixie
Still very early development and basic features when I last looked at it though.

To walk forward the foot has to move forward, then the body follow it.
This isn't doing that, the feet are just moving up-and-down. It is more like an Irish dance than a walk.

Pro Motion is in the vein of Amiga pixel editors like Deluxe Paint or GrafX2 so if you aren't used to how they work it can be a bit to get your head around.

You can use the fill tool with "Isolated fill" unchecked to replace all pixels of an index.

There's an "Erase" painting mode which paints with the layer transparent colour, but I find it's easier just use regular paint mode and select the transparent colour from the palette.

There is a "Selection" mask painting mode, but no floating, and not even a selection-to-brush function that I can find (which I think there really should be).

Pro Motion is strictly indexed so no truecolour editing.

There's "Brush Resize" (Ctrl+Z) which allows you to click and drag to resize the brush on the canvas. There's a brush size spin/slider in the beta version, but not yet in the release version.

Also try checking "My Documents\GaleBackup" for previous versions.