I here you with the classic light notepad look. Xournals A4 sheets looks pretty neat.. I would suggest a preference setting for "theme - light or dark" or as you say a fill/bacground color. Its of minor priority though.

kinetic handtool would have been great... a "floating" width/height of the sketch area would be awesome aswell..

I really appreciate your work thp. I am a true panucci and gpodder fan ;-)

please tell me how or if I can assist you further...on any project