2021 Update: Background size is supported by most major browser but if your mobile browsers doesn’t support it use zoom.
You could use background-size, as its supported by most browsers (but not all http://caniuse.com/#search=background-size)
background-size : 150% 150%;
Or
You can use a combo of zoom for webkit/blink/ie and transform:scale for Mozilla(-moz-) and old Opera(-o-) for cross-browser desktop & mobile
[class^="icon-"]{
display: inline-block;
background: url('../img/icons/icons.png') no-repeat;
width: 64px;
height: 51px;
overflow: hidden;
zoom:0.5;
/* Mozilla support */
-moz-transform:scale(0.5);
-moz-transform-origin: 0 0;
}
.icon-big{
zoom:0.60;
/* Mozilla support */
-moz-transform:scale(0.60);
-moz-transform-origin: 0 0;
}
.icon-small{
zoom:0.29;
/* Mozilla support */
-moz-transform:scale(0.29);
-moz-transform-origin: 0 0;
}