It's a parameter issue.
'function changePic(one, two, three)'
should just be
'function changePic(picture)'
And the switch should be something along the lines of:
if (picture == "one")
{
document.getElementById(one).src = x;
}
etc,
The function takes three parameters (one, two, three) and you're only plugging in a single parameter (one), (two), or (three). Also, you're plugging in strings, and the switch is checking for variables.
That is to say, "one" does not equal one.
one is a variable name "one" is a string value.