Aqui mostra o comparativo entre o arquivo FXML quando aberto no scenebuilder e quando compilo!
todas as imagens não carregam(BG, icones e a logo!)
Eu achei um tópico falando que é um bug do JDK mas não encontrei uma solução. Meu inglês também não ajuda muito!
FXML
<Button fx:id="menuItem02" alignment="CENTER_RIGHT" maxHeight="1.7976931348623157E308" maxWidth="230.0" mnemonicParsing="false" onAction="#showSubmenu" styleClass="menu-bt" text="Editor">
<graphic>
<ImageView fitHeight="15.0" fitWidth="15.0" pickOnBounds="true" preserveRatio="true" styleClass="menu-icon">
<image>
<Image url="@../../assets/editor.png" />
</image>
</ImageView>
</graphic>
</Button>
<Button fx:id="menuItem03" alignment="CENTER_RIGHT" maxHeight="1.7976931348623157E308" maxWidth="230.0" mnemonicParsing="false" onAction="#showSubmenu" styleClass="menu-bt" text="Mods (Alpha)" textAlignment="RIGHT">
<graphic>
<ImageView fitHeight="15.0" fitWidth="15.0" pickOnBounds="true" preserveRatio="true" styleClass="menu-icon">
<image>
<Image url="@../../assets/mods.png" />
</image>
</ImageView>
</graphic>
</Button>
<Button fx:id="menuItem04" alignment="CENTER_RIGHT" maxHeight="1.7976931348623157E308" maxWidth="230.0" mnemonicParsing="false" onAction="#showSubmenu" styleClass="menu-bt" text="Settings">
<graphic>
<ImageView fitHeight="15.0" fitWidth="15.0" pickOnBounds="true" preserveRatio="true" styleClass="menu-icon">
<image>
<Image url="@../../assets/settings.png" />
</image>
</ImageView>
</graphic>
</Button>
<Button fx:id="menuItem05" alignment="CENTER_RIGHT" maxHeight="1.7976931348623157E308" maxWidth="230.0" mnemonicParsing="false" onAction="#showSubmenu" styleClass="menu-bt" text="About">
<graphic>
<ImageView fitHeight="15.0" fitWidth="15.0" pickOnBounds="true" preserveRatio="true" styleClass="menu-icon">
<image>
<Image url="@../../assets/info.png" />
</image>
</ImageView>
</graphic>
</Button>
<Button fx:id="menuItem06" alignment="CENTER_RIGHT" maxHeight="1.7976931348623157E308" maxWidth="230.0" mnemonicParsing="false" onAction="#showSubmenu" styleClass="menu-bt" text="Quit">
<graphic>
<ImageView fitHeight="15.0" fitWidth="15.0" pickOnBounds="true" preserveRatio="true" styleClass="menu-icon">
<image>
<Image url="@../../assets/quit.png" />
</image>
</ImageView>
</graphic>
</Button>
</children>
<padding>
<Insets top="100.0" />
</padding>
</VBox>
<!-- end.MENU -->
<VBox fx:id="submenu" prefHeight="200.0" prefWidth="30.0" styleClass="submenu-container">
</VBox>
<!-- end.SUBMENU -->
</children>
</HBox>
<!-- end.SIDEBAR -->
</left>
<center>
<VBox alignment="CENTER" prefHeight="200.0" prefWidth="100.0" BorderPane.alignment="CENTER" styleClass="start-screen ">
<children>
<ImageView fitHeight="150.0" fitWidth="500.0" pickOnBounds="true" preserveRatio="true">
<image>
<Image url="@../../assets-raw/logo.png" />
</image>
</ImageView>
</children>
</VBox>
</center>
</BorderPane>
<!-- LIGHT EFFECT -->
<Rectangle arcHeight="5.0" arcWidth="5.0" blendMode="OVERLAY" focusTraversable="true" height="900.0" mouseTransparent="true" stroke="BLACK" strokeType="INSIDE" strokeWidth="0.0" width="1440.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<fill>
<RadialGradient centerX="0.5168067226890757" centerY="0.5" radius="0.5">
<stops>
<Stop color="TRANSPARENT" />
<Stop color="TRANSPARENT" offset="0.2569832402234637" />
<Stop color="#00000061" offset="1.0" />
</stops>
</RadialGradient>
</fill>
<cursor>
<Cursor fx:constant="DEFAULT" />
</cursor>
</Rectangle>
</children>