You can add a ContextMenu to any control by using control's ContextMenu property. For example, this code adds a ContextMenu to a Rectangle.
<Window x:Class="ContextMenuWPFSample.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<Canvas >
<Rectangle Name="BlueRectangle"
Width="200" Height="100"
Canvas.Left="20" Canvas.Top="20"
Fill="LightBlue">
<Rectangle.ContextMenu>
<ContextMenu Name="RectangleMenu">
<MenuItem Header="Color">
<MenuItem Header="Red" Click="RedMenuItem_Click" />
<MenuItem Header="Green" Click="GreenMenuItem_Click"/>
<MenuItem Header="Orange" Click="OrangeMenuItem_Click"/>
</MenuItem>
</ContextMenu>
</Rectangle.ContextMenu>
</Rectangle>
</Canvas>
</Window>