Those purple lights could be animated to blink at a low frequency so that players notice them as a nice feature but not until it distracts the player.Again, idea borrowed from Jazz Jackrabbit games.
@SoFDMC That's a nice idea. At the moment though the light is a part of the tile so animation isn't exactly possible. However I might actually make the light a separate entity which would enable me to animate it.Come to think of it, all the alpha effects should have their own layer. Its something to think about