Standing with both arms down, palms open to the front. I'm afraid I don't what this one represents. Standing with both hands crossing over his chest. I'm afraid I don't know what that one means either. Standing with one arm down and one up and the open palm up in front like a stop signal. I do know this one.
This signifies a story in the scriptures where the Buddha became aware that people were feuding over the water in the river. It was a very bad drought and two opposing people on two sides of the river wanted the water. They had decided to go to war against each other to have the water in the river. So at that time the Buddha decided to go and try to stop them warring. He was able to talk to these people and said: "What is more important, the water or the blood of the people, blood flowing in the river?" So he was basically asking them to stop thinking of going to war. That's the meaning of the statue with the Buddha holding his hand up.
Fortunately they were able to listen to the Buddha at the time and decided to share the water rather than go to war against each other. I think it may have helped that one of the groups of people happened to be his clan, so they were able to listen to him.
I will have to find out about the other ones. It might be quite interesting because most of the Buddha statues do mean something. Such as the sitting statue here with his hand touching the ground is the moment of his enlightenment where he called the earth to witness, to say he had the right to sit there just the moment before his enlightenment. I think it signifies the complete letting go of doubt and believing that he had the right to become enlightened and that he would become enlightened.