Edit in JSFiddle

var arrCharacters = [];
for (var i = "a".charCodeAt(0); i <= "z".charCodeAt(0); i++)
	arrCharacters.push(String.fromCharCode(i));
for (var i = "A".charCodeAt(0); i <= "Z".charCodeAt(0); i++)
	arrCharacters.push(String.fromCharCode(i));
for (var i = 0; i <= 9; i++)
	arrCharacters.push(i);
window.onload = function() {
	var oPlaceholder = document.getElementById("placeholder");
	oPlaceholder.innerHTML = "";
	for (var i = 0; i < 10; i++) {
		var imgSrc = GetRandImage();
		var rawHTML = "<a href=\"" + imgSrc + "\" style=\"font-weight: bold;\">" + imgSrc + "</a><br /><img src=\"" + imgSrc + "\" /><hr />";
		oPlaceholder.innerHTML += rawHTML;
	}
}

function GetRandImage() {
	var randKey = "";
	for (var i = 0; i < 5; i++)
		randKey += arrCharacters[Math.floor(Math.random() * arrCharacters.length)];
	return "http://i.imgur.com/" + randKey + ".jpg";
}