I use a lot inkscape to create this kind of presenting images. All was done with simple operations and in one layer. Nothing fancy or complicated. The idea was to create a simple Skeumorphism design to mimic traditional concept art style. You can download freely from mypaint program. Si lees español esta fue la noticia: http://www.ramonmiranda.com/2011/09/mypaint-concept-design-set-es.html
This is an idea that devs are already working on. I use SVG to play al ot with the shapes and location of elements . do you find it useful? give them feedback then and help them :D.
You know i love brushes creation, so i spend lot of time creating them and tweaking them. These are only 4 ideas that i suggest to improve a bit the brushes creation environment.