CSS radial menu

Here's a solution if you only needed 'four quarters', rather than an unknown amount:

.wrap {
  position: relative;
  height: 310px;
  width: 310px;
}
.square {
  display: inline-block;
  height: 150px;
  width: 150px;
}
.circle {
  position: absolute;
  height: 180px;
  width: 180px;
  top: 50%;
  left: 50%;
  background: gray;
  border-radius: 50%;
  transform: translate(-50%, -50%);
  border: 10px solid white;
}
.wrap div:hover {
  background: url(http://placekitten.com/g/300/300);
  background-size: 100% 100%;
}
.square:nth-child(1) {
  border-radius: 100% 0 0 0;
  background: cornflowerblue;
}
.square:nth-child(2) {
  border-radius: 0 100% 0 0;
  background: tomato;
}
.square:nth-child(3) {
  border-radius: 0 0 0 100%;
  background: darkorange;
}
.square:nth-child(4) {
  border-radius: 0 0 100% 0;
  background: green;
}

<div class="wrap">
  <div class="square"></div>
  <div class="square"></div>
  <div class="square"></div>
  <div class="square"></div>
  <div class="circle"></div>
</div>

Here's an alternative, less fancy, have to get clever with img opacity + div background-color to preserve the hover.

/* CSS */
* { 
  box-sizing: border-box;
}
div {
  background: white;
}
img {
  width: 100%;
  -webkit-transition: opacity .2s;
}
div:hover > img {
  opacity: .5;
}
.wrap,
.wrap div:first-child{
  width: 500px;
  height: 500px;
  margin: auto;
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
}
.wrap div:first-child {
  float: none;
  z-index: 2;
  width: 50%;
  height: 50%;
  border-radius: 100%;
  border: 30px solid white;
}
div div {
  float: left;
  overflow: hidden;
  width: 50%;
  height: 50%;
  border: 15px solid white;
}
div div:nth-child(2) img {
  border-radius: 100% 0 0 0;
}
div div:nth-child(3) img {
  border-radius: 0 100% 0 0;
}
div div:nth-child(4) img {
  border-radius: 0 0 0 100%;
}
div div:nth-child(5) img{
  border-radius: 0 0 100% 0;
}

<!-- HTML -->
<div class="wrap">
    <div><img src="http://placehold.it/300x300&text=Center" /></div>
    <div><img src="http://placehold.it/300x300&text=Top Left" /></div>
    <div><img src="http://placehold.it/300x300&text=Top Right" /></div>
    <div><img src="http://placehold.it/300x300&text=Bottom Left" /></div>
    <div><img src="http://placehold.it/300x300&text=Bottom Right" /></div>
</div>

I made this pen with a css radial menu. The circular menu appears on hover :

Demo : CSS radial menu

The radial shape is made with border radius and the overflow property. The hover animation is handled with CSS transition (scale and oapcity).

For a version with menu titles, see this DEMO

Full Code for the radial menu :

HTML :

<span><span></span></span>
<div class="wrap">
  <a href="#"><div></div></a>
  <a href="#"><div></div></a>
  <a href="#"><div></div></a>
  <a href="#"><div></div></a>
  <a href="#"><div></div></a>
</div>

CSS :

body,html{margin:0;padding:0;height:100%;}
body{background:#E3DFD2;box-shadow: inset 0 0 20vmin 0 #585247;}
.wrap{
  position:relative;
  width:80vmin; height:80vmin;
  margin:0 auto;
  background:inherit;
  transform:scale(0.2) translatez(0px);
  opacity:0;
  transition:transform .5s, opacity .5s;
}
a{
  position:absolute;
  left:0; top:0;
  width:47.5%; height:47.5%;
  overflow:hidden;
  transform:scale(.5) translateZ(0px);
  background:#585247;
}
a div{
  height:100%;
  background-size:cover;
  opacity:.5;
  transition:opacity .5s;
  border-radius:inherit;
}
a:nth-child(1){
  border-radius:40vmin 0 0 0;
  transform-origin: 110% 110%;
  transition:transform .4s .15s;
}
a:nth-child(1) div{
  background-image:url('https://farm3.staticflickr.com/2827/10384422264_d9c7299146.jpg');
}
a:nth-child(2){
  border-radius:0 40vmin 0 0;
  left:52.5%;
  transform-origin: -10% 110%;
  transition:transform .4s .2s;
}
a:nth-child(2) div{
  background-image:url('https://farm7.staticflickr.com/6083/6055581292_d94c2d90e3.jpg');
}
a:nth-child(3){
  border-radius:0 0 0 40vmin;
  top:52.5%;
  transform-origin: 110% -10%;
  transition:transform .4s .25s;
}
a:nth-child(3) div{
  background-image:url('https://farm7.staticflickr.com/6092/6227418584_d5883b0948.jpg');
}
a:nth-child(4){
  border-radius:0 0 40vmin 0;
  top:52.5%; left:52.5%;
  transform-origin: -10% -10%;
  transition:transform .4s .3s;
}
a:nth-child(4) div{
  background-image: url('https://farm8.staticflickr.com/7187/6895047173_d4b1a0d798.jpg');
}
a:nth-child(5){
  width:55%;height:55%;
  left:22.5%; top:22.5%;
  border-radius:50vmin;
  box-shadow:0 0 0 5vmin #E3DFD2;
  transform:scale(1);
}
a:nth-child(5) div{
  background-image: url('https://farm4.staticflickr.com/3766/12953056854_b8cdf14f21.jpg');
}
span{
  position:relative;
  display:block;
  margin:0 auto;
  top:45vmin;
  width:10vmin; height:10vmin;
  border-radius:100%;
  background:#585247;
  transform:translateZ(0px);
}
span span{
  position:absolute;
  width:60%;height:3px;
  background:#ACA696;
  left:20%; top:50%;
  border-radius:0;
}
span span:after, span span:before{
  content:'';
  position:absolute;
  left:0; top:-1.5vmin;
  width:100%; height:100%;
  background:inherit;
}
span span:after{
  top:1.5vmin;
}
span:hover + .wrap, .wrap:hover{
  transform:scale(.8) translateZ(0px);
  opacity:1;
}
span:hover + .wrap a, .wrap:hover a{
  transform:scale(1) translatez(0px);
}
a:hover div{
  opacity:1;
  transform:translatez(0px);
}