it does not have to be BMP, can be PNG too, for example.
it can also be 32bit (including transparency), if you like.
maybe just a neon-green/-yellow K on black background?
As i see it, it does not have to be artistically, but it has to allow the user to instantly know what this thing in the task-bar is (without reading text even).
Not sure if putting stuff in front of the spring logo works so well.
Yes, I did it too but in the end the red/white sun does not mean much to players. If you get rid of it, you could gain a few pixels to make the bit/sphere a bit more detailed.