This is how I ended up coding it thanks to your recommendations (the imageSource for the background image is set in C# programmatically and works):
<Border BorderThickness="1" CornerRadius="5" Height="94" Width="175.5"
HorizontalAlignment="Left" VerticalAlignment="Center" Margin="3,3,0,3">
<Border.Background>
<ImageBrush x:Name="myImg" Stretch="Fill"/>
</Border.Background>
<Border.Effect>
<DropShadowEffect BlurRadius="10" ShadowDepth="7" Direction="315"/>
</Border.Effect>
<Border.BorderBrush>
<LinearGradientBrush EndPoint="0.811,0.2" StartPoint="0.246,1.023">
<GradientStop Color="#FF7C9FC8" Offset="0"/>
<GradientStop Color="#FF7C9FC8" Offset="1"/>
<GradientStop Color="#FF353535" Offset="0.491"/>
</LinearGradientBrush>
</Border.BorderBrush>
<Border BorderThickness="0" CornerRadius="0" Margin="0" >
<Border.Background>
<RadialGradientBrush GradientOrigin="0.7,-0.6" RadiusY="0.5" RadiusX="1.001">
<RadialGradientBrush.RelativeTransform>
<TransformGroup>
<ScaleTransform CenterY="0.5" CenterX="0.5" ScaleY="1" ScaleX="1"/>
<SkewTransform AngleY="0" AngleX="0" CenterY="0.5" CenterX="0.5"/>
<RotateTransform Angle="-29.285" CenterY="0.5" CenterX="0.5"/>
<TranslateTransform/>
</TransformGroup>
</RadialGradientBrush.RelativeTransform>
<GradientStop Color="#B6FFFFFF"/>
<GradientStop Color="#0BFFFFFF" Offset="0.578"/>
</RadialGradientBrush>
</Border.Background>
</Border>
</Border>