I started with a bullet physics simulation, and did a smoke simulation to trail the bullet.
After that, I created a simple background using procedural textures and UV information. No image texture, no nothing, and yet this picture is one of my favorite wallpapers ever. Inspiration was pulled from a Muse album cover.
I then mixed the two together in Gimp, fixed the smoke, and added the Blenderfire logo.
After that, I moved to Krita, and painted all the advanced painting and fades and splatters you see. The final image?
Sorry, but to give the picture credit I left it at full resolution. Enjoy!