Thomas,
Do you really need to draw a single pixel? Or are you wanting to draw a line of pixels?
I ask because writing to the LCD involves a certain amount of overhead. Each time you want to write data to the LCD you define a rectangle of interest. Then you send the data. If you're plotting single pixels, each pixel must be set up individually and this takes a small but cumulative amount of time. If you're wanting to draw a horizontal or vertical line, or even a rectangular area, you can set up the area of interest and just dump the data, two bytes for each pixel.
Thanks,
Dale Wheat