[ruslan_mart]

CSS:

.slider_img img {
   display: none;
}

HTML:

<div class="slider_img">
   <img src="/uploads/usertemplates/slider1.png">
   <img src="/uploads/usertemplates/slider2.png">
   <img src="/uploads/usertemplates/slider3.png">
</div>

<input type="button" onclick="slider(false)" value="Prev" />
<input type="button" onclick="slider(true)" value="Next" />

JS:

var sliderIndex = -1, imgs = $('.slider_img img');

function slider(a) {
   sliderIndex += a ? 1 : -1;
   if(!imgs[sliderIndex]) sliderIndex = a ? 0 : imgs.length -1;
   imgs.css('display', 'none');
   imgs.eq(sliderIndex).css('display', '');
}

Не проверял, но работать должно.