Bitmap of the particle (if any).
When the particle has no bmap, it is a colored dot, taken from an internal image that also contains the default font. This font can be replaced by providing an external ackfont.pcx image. Note that this will also replace the default particle image, which is taken from position (100,56) of the ackfont.pcx image.
lifespan, x,y,z, vel_x, gravity, size, alpha, red,green,blue, bmap, BRIGHT, TRANSLUCENT, MOVE, STREAK, event, skills, effect