I would not bother with the queue; I would simply map the ADC values (X and Y) into a 2D pixel array, accumulating a "bright" pixel value to the existing value at the pixel location, and periodically decimate the pixel values (e.g. divide all pixel values by 2 every 1/10th of a second) which should give you a nice emulation of phosphor decay. You can tune the decimation schedule to get a pleasing decay period according to your pixel bit depth, and the update rate of your output device.
-- Jeff Dutky
