Those look good. It looks like you learned to paint with a brush before you started digital painting - your paintings have that 'painterly' layered look that you learn when painting with pigments.
It has been a long time since I watched Bob Ross, but he always impressed me with how relaxed he was while painting and yet he produced a complete painting during a 25 minute show. I can see his influence in your paintings.
My current favorite foliage brushes are from LFJHutch:
http://ljfhutch.deviantart.com/art/Gimp ... -244293974He also wrote a tutorial on how he uses them in GIMP:
http://ljfhutch.deviantart.com/art/Foli ... -244308242GIMP Paint Studio (
http://code.google.com/p/gps-gimp-paint-studio/ ) has a collection of brushes, palettes, etc. aimed at helping the traditional artist adjust to digital painting. You might want to check them out as well.