Pure CSS gallery markup example

<div class="gallery">
 <input type="radio" name="chk" class="chkbox chkbox1" id="chk1" checked><label  for="chk1"><img alt="gallery" src="/resources/collection/1.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox2" id="chk2"><label  for="chk2"><img alt="gallery" src="/resources/collection/2.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox3" id="chk3"><label  for="chk3"><img alt="gallery" src="/resources/collection/3.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox4" id="chk4"><label  for="chk4"><img alt="gallery" src="/resources/collection/4.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox5" id="chk5"><label  for="chk5"><img alt="gallery" src="/resources/collection/5.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox6" id="chk6"><label  for="chk6"><img alt="gallery" src="/resources/collection/6.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox7" id="chk7"><label  for="chk7"><img alt="gallery" src="/resources/collection/7.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox8" id="chk8"><label  for="chk8"><img alt="gallery" src="/resources/collection/8.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox9" id="chk9"><label  for="chk9"><img alt="gallery" src="/resources/collection/9.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox10" id="chk10"><label  for="chk10"><img alt="gallery" src="/resources/collection/10.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox11" id="chk11"><label  for="chk11"><img alt="gallery" src="/resources/collection/11.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox12" id="chk12"><label  for="chk12"><img alt="gallery" src="/resources/collection/12.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox13" id="chk13"><label  for="chk13"><img alt="gallery" src="/resources/collection/13.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox14" id="chk14"><label  for="chk14"><img alt="gallery" src="/resources/collection/14.jpg"></label>
 <input type="radio" name="chk" class="chkbox chkbox15" id="chk15"><label  for="chk15"><img alt="gallery" src="/resources/collection/15.jpg"></label>
<img alt="gallery" src="/resources/collection/1.jpg" class="bgimg" id="chkbox1">
<img alt="gallery" src="/resources/collection/2.jpg" class="bgimg" id="chkbox2">
<img alt="gallery" src="/resources/collection/3.jpg" class="bgimg" id="chkbox3">
<img alt="gallery" src="/resources/collection/4.jpg" class="bgimg" id="chkbox4">
<img alt="gallery" src="/resources/collection/5.jpg" class="bgimg" id="chkbox5">
<img alt="gallery" src="/resources/collection/6.jpg" class="bgimg" id="chkbox6">
<img alt="gallery" src="/resources/collection/7.jpg" class="bgimg" id="chkbox7">
<img alt="gallery" src="/resources/collection/8.jpg" class="bgimg" id="chkbox8">
<img alt="gallery" src="/resources/collection/9.jpg" class="bgimg" id="chkbox9">
<img alt="gallery" src="/resources/collection/10.jpg" class="bgimg" id="chkbox10">
<img alt="gallery" src="/resources/collection/11.jpg" class="bgimg" id="chkbox11">
<img alt="gallery" src="/resources/collection/12.jpg" class="bgimg" id="chkbox12">
<img alt="gallery" src="/resources/collection/13.jpg" class="bgimg" id="chkbox13">
<img alt="gallery" src="/resources/collection/14.jpg" class="bgimg" id="chkbox14">
<img alt="gallery" src="/resources/collection/15.jpg" class="bgimg" id="chkbox15">
</div>