Great pics! I've had a few encounters with garter breeding balls--one was right under a townhouse I was renting in the far exurbs, surrounded by forest. I heard the neighbors screaming early on a Sunday morning and ran outside, only to find a big ball right on my front porch! I ended up keeping the first male to break away from the ball, on the grounds that the Darwinian odds were against him anyway. He was a gentle snake, I named him Romeo because of how I found him, but the three big females in this ball were the meanest Juliets I've ever seen. They each refused to leave after the gentlemen departed and coiled up under the garden hose and hedges, hissing and striking at anything that came near for the rest of the morning. I have great pics of this but unfortunately none digital.
I also had a big gravid female give birth in my hands one morning. I couldn't ID gravid females by sight back then--she was just the biggest garter I had ever seen and I rished to pick her up! When I realized what I was interrupting I backed away quietly, but I must say it was a pretty amazing experience!