Dudemullet: One of the challenges (and interesting) parts about working with 16×16 is the forced limitation. Unfortunitly some of the sprites you requested won’t work well because they are large. The characters in Kung Fu for example are relatively huge, take for example the sprite below.
Same kind of goes for excitebike and the Mario cape flying, it becomes an issue of what to crop.
You can get creative and have panning effects, take the sprite below of the caped koopa flying by. this sprite is more than 16 pixels wide, but because it flys through the frame, you can cheat it a little.
Lastly, I updated the mario coin for a darker background.
Fogleman, that is amazing!