This might help http://jsfiddle.net/m4xbf/
HTML
<form name="field" method="post" id="form">
<label for="username">Username:</label>
<br/>
<input name="username" id="username" type="text" /> <span id="img"></span>
<span id="img2"></span>
<br/>
<br/>
<input name="submit" type="button" value="Register" id="submit" />
<br/>
<br/>
</form>
jQuery
$(document).ready(function(){
$("input[type=text]").blur(function () {
$("#img").append("<img src='http://loadinggif.com/images/image-selection/29.gif' width='20' height='20' alt=''/>").fadeIn(500).delay(1000).fadeOut(500, function () {
$("#img").empty().append("<img class='image1' src='https://cdn1.iconfinder.com/data/icons/essen/32/check.png' width='20' height='20' alt=''/>").fadeIn(500).delay(1000).fadeOut(500);
});
});
});