In Uibinder specify your image on src attribute of <ui:image> tag,
Inside the <ui:style> attribute specify your @sprite.backgroundPicture
tag. Try the below example.
S. Abraham
www.DataStoreGwt.com
Persist objects directly in Google App Engine
<?xml version="1.0" encoding="UTF-8"?>
<ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'>
<ui:image field='backgroundPicture' src='easyxbrl_logo_1.png' />
<ui:style>
@sprite .backgroundPicture {
gwt-image: 'backgroundPicture';
float: left;
margin-top:5px;
margin-bottom:5px;
margin-left: 50px;
}
</ui:style>
<g:LayoutPanel styleName="{style.backgroundPicture}"/>
</ui:binder>