You can do it the following way
HTML
<img id="my_image" src="http://i.imgur.com/tL6nW.gif" alt="">
<br>
<input class="radio" type="radio" name="radio" value="http://i.imgur.com/tL6nW.gif" checked>Image1<br>
<input class="radio" type="radio" name="radio" value="http://i.imgur.com/BfZ5f.gif">image2
</form>
JS
$('.radio').on({
'click': function(){
var image_url=$(this).val();
$('#my_image').attr('src',image_url);
}
});
Here is a JsFiddle
If you want to make it completely dynamic you can initialize the image element's default image at the page loading time too. The additional code will be something like this.
$(document).on('ready',function(){
$('#my_image').attr('src','default.gif');
});