Please share the your code firstly .. I guess you want like this :
<head><title>Image Display Test
</title>
<script type="text/javascript">
</script>
</head>
<body>
<input type="button" value="Show Button" onclick="showImage();"/>
<img id="loadingImage" src="yourimage.gif" style="visibility:hidden"/>
</body>
Thanks,
Ambesha