Maybe you could accomplish that by leaving it unpolished, unfinished somehow? I don't know if you use blur, smudge or how does one really paint digitally at all Maybe some steps in this progression convey that pictoric sketchiness more than the finished piece. But again, I don't think your technique lacks anything Something else I liked and forgot to mention is how you framed this and how the black, empty space is part of the composition.
I use blur and smudge a lot by the end of a painting. (Which I know is something that some digital artists really don't like. But hey, to each their own.) I find that trying to leave my stuff "unpolished, unfinished somehow" just looks, well, unpolished and unfinished. I really admire the way that some artists make the sketchiness and visible brushstrokes of their work look purposeful and beautiful. I'll just have to keep practicing.
I'll be the first to admit that I don't usually give much thought to composition and its meaning beyond what I think simply "looks good." But this once, I actually did include the extra negative space intentionally. I'm glad you like it.
I know very little of digital painting, but I think blur/smudge is a great tool. Specially for color blending and such. I guess many people don't even know how to use it properly. I was reading something *nebezial said about it, and how some people think color blending can't even be done in photoshop, and they chose other programs to paint because of that. I think it's cool you're "not afraid" of these tools and you have a style of your own. I suppose there's always room for improvement and experimentation, of course, and that's also part of the beauty of it.