8x1 Lightning Sprite Texture

GIMP:

1. Draw some lines like this: | | |
2. Fill every second white space with black (if you don't do this, your lightnings will look doubled)
3. Filters - Distorts - IWarp - Warp around a bit
4. Filters - Render - Clouds - Difference Clouds - Details = 15
5. Colors - Invert
6. Colors - Levels - Play around with the Input Sliders until you have some nice result (I used something around 80, 0.2, 255 but try until you are happy with the result)
7. Colors - Colorize - Choose some color with the "Hue" slider and a high saturation with the saturation slider
8. Colors - Color to Alpha - Choose black
9. Clean up
10. [Optional] Filters - Map - Make Seamless

With some texture animation it may look like this:

http://www.youtube.com/watch?v=F7Y-wMTJZnk