Hi Amol111,
To fetch id of selected image you have to use OnClientItemSelected event. And from that to get id use the value property.
Below line of code gives you the id of selected item.
var value = employees[idx]._value;
To add scrollbar to list you have to use OnClientPopulated event and apply the style property to the get_completionList like below.
function Employees_Populated(sender, e) {
var employees = sender.get_completionList().childNodes;
// Assigning style property.
sender.get_completionList().style.maxHeight = "100px";
sender.get_completionList().style.overflowX = "hidden";
sender.get_completionList().style.overflowY = "auto";
for (var i = 0; i < employees.length; i++) {
var div = document.createElement("DIV");
div.innerHTML = "<img style = 'height:50px;width:50px' src = 'photos/" + employees[i]._value + ".jpg' /><br />";
employees[i].appendChild(div);
}
}