You can easily achieve this using a few of the options for the slideshow:
First, let's add the login box, in my example it has id login
and we will also tell the plugin to select the slides based on the selector '> div.cycle-slide' so that the login div isn't considered a slide. Lastly, we just need to make sure and set the z-index of the login box to be above the slides.
Example: http://jsfiddle.net/lucuma/87FUR/3/
HTML:
<div class="cycle-slideshow item" data-cycle-timeout="3000" data-cycle-speed="2000" data-cycle-slides="> div.cycle-slide" data-cycle-fx="fade">
<div id="login">Your Login here</div>
<div class="cycle-slide">
<img src="http://placehold.it/550x550/" />
</div>
<div class="cycle-slide">
<img src="http://placehold.it/550x550/ff0000" />
</div>
<div class="cycle-slide">
<img src="http://placehold.it/550x550/" />
</div>
</div>
CSS:
div.cycle-slideshow {
width: 550px;
height: 550px;
}
#login {
position: absolute;
width: 200px;
height: 400px;
background-color:blue;
top: 0;
z-index: 99999;
opacity: .5;
}
img {
display:block;
max-width:100%;
}