废话少说，直接代码

---

applyBG = function( v ){
    v.onDrawBackground = function( hdc,rc ){
        a1 = ::POINTF( 0,0 );
        a2 = ::POINTF( rc.width(),rc.height() );
        b = gdip.lineBrush( 
            a1,
            a2,
            0xFF315e95,
            0xFF228ba2
        ); 
        b1 =  gdip.solidBrush( 0x22000000 );
        gg = gdip.graphics(hdc);
        gg.fillRectangle( b, 0,0, rc.width(), rc.height() );
        gg.fillPolygon( b1, , ::POINTF( 0,0 ),
                              ::POINTF( rc.width()*0.33,0 ),
                              ::POINTF( 0,rc.height()*0.6 )
         );
         gg.fillPolygon( b1, , ::POINTF( 0,0 ),
                              ::POINTF( rc.width(),0 ),
                              ::POINTF( rc.width(),rc.height()*0.8 ),
                              ::POINTF( 0,rc.height()*0.3 )
         );
    }
}

applyBG( winform );

具体新建一个新窗体，贴进去就好了。