I really don´t know when this bug came out, but Blogger no longer allows to add Image gadgets to your blog layout, if you don´t specify a title text. So, you cannot add a plain image with a link, as if it was a button, what is quite inconvenient…
When you try to add the gadget, the helper pops up with the following window:
And it will keep saying that Title is a required field. Well, the workaround for that, is to put the following text as title:
<!-- -->
It´s an HTML comment tag, that will fool the gadget helper allowing you to continue, but still won’t show any title.
Hope it helps !!!