Spike is obviously a lot smaller in this picture than he was in the last one, but the show has established that his size can change rather quickly and Twilight does have the power to make him bigger (even if the one time she did it, it was done by accident). So you can either take it that way, or this being a younger Spike. Whatever you prefer.
Once again I played around with Spike appearance, I wanted him to look fierce, but not to fierce. He’s still Spike after all.
This is a scene of a battle with an off screen enemy like the last one. Whoever they’re battling, I’ll leave to your imagination.