How to bind a StackLayout

I have a View Model returning a object.

I can bind one ListView, like this:

<ListView x:Name="listViewBannerPrincipal" ItemsSource="{Binding banner}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell>
                <ViewCell.View>
                    <StackLayout Orientation="Horizontal">
                        <Image Source="{Binding imagemURL}"></Image>
                    </StackLayout>
                </ViewCell.View>
            </ViewCell>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>`

But I want bind my StackLayout. I tried:

<StackLayout>
    <Image Source="{Binding imagemURL}"></Image>
</StackLayout>

Is not working because my ViewModel returns a object Banner.

How can I bind my Image?