Modificar el CSS del Uploader Media WordPress +3.5
Uploader Media Wordpress
.media-menu,.attachments-browser,.media-frame-menu,#wp\_editimgbtn,.media-router .active:after {
display:none;
}
.media-modal{
width:600px;
max-height:400px;
margin:auto;
}
.media-frame-title h1{
font-family:"gill sans";
}
.media-frame-title,.media-frame-router,.media-frame-toolbar{
left:0px;
text-align:center;
}
.media-frame-content,.uploader-inline-content{
margin-top:40px;
position:static;
text-align:center;
}
.media-toolbar,.media-toolbar-primary{
position:static;
width:128px;
padding:0px;
margin:auto;
float:none;
text-align:center;
}
media-button-insert{
display:block;
}
.media-router{
float:none;
width:100px;
margin:auto;
}
.media-router a{
border-right:0px;
}
Fuente: Customize Media Manager https://wordpress.org/support/topic/customize-media-manager?replies=5