What about:
$("img.imgexpander").click
(
function()
{
var expandableDIVs = $(this)
.parents("div.bigdiv:first")
.find("div.expand");
expandableDIVs.toggle();
this.src = expandableDIVs.is(":visible") ? "img2.png" : "img1.png";
}
);
IMG imgexpander. DIV . src , DIV, "div.expand".
, jQuery DIV, div.expand, JavaScript .
this DOM, "img.imgexpander". , .
EDIT. div.expand , OP. DIV, DIV, img.
, , . , IMG DIV - bigdiv, . :first.