img{opacity: 1;
-webkit-transition: 1.0s;
-moz-transition: 1.0s;}
img:hover{opacity: .70;}

Efecto blur:

img{-webkit-transition: 1.0s;
-moz-transition: 1.0s;
filter: blur(2px);
-webkit-filter: blur(2px);
-moz-filter: blur(2px);}
img:hover{
filter: none;
-webkit-filter: blur(0px);
-moz-filter: blur(0px);
filter:progid:DXImageTransform.Microsoft.Blur(PixelRadius='0');}

Efecto background doble:

img{
opacity: 0.79;
padding:15px;
-webkit-transition-duration: .99s;
-moz-transition-duration: .99s;
transition-duration: .99s;
background:url(URL DEL BACKGROUND);}

img:hover{opacity: 0.99;
border-radius:10px;
-webkit-transition-duration: .99s;
-moz-transition-duration: .99s;
transition-duration: .99s;
background:url(URL DEL BACKGROUND);

Espero que os haya gustado esta serie de efectos para tus imágenes <3
Créditos: Afiqah Junizan

グッドラック！