You can create a tiled background with the specified content.

[TemplatePart(Name = ElementRoot, Type = typeof(Border))]
[ContentProperty(nameof(Content))]
public class Watermark : Control

Attributes

Property	Description	Default Value	Remarks
Angle	Watermark rotation angle	20	provided by default style
Content	Content that needs to use watermark
Mark	Watermark
MarkWidth	Watermark width	0
MarkHeight	Watermark height	0
MarkBrush	Watermark color
AutoSizeEnabled	Whether the watermark is automatically adapted to the size	true
MarkMargin	Watermark Margin

Case

 <hc:UniformSpacingPanel VerticalAlignment="Center" Margin="32" ChildWrapping="Wrap" Spacing="16" ItemWidth="256" ItemHeight="128">
<hc:Watermark Mark="HandyControl">
    <Border BorderThickness="1" CornerRadius="4" BorderBrush="{DynamicResource BorderBrush}" />
</hc:Watermark>
<hc:Watermark Mark="HandyControl" FontSize="30">
    <Border BorderThickness="1" CornerRadius="4" BorderBrush="{DynamicResource BorderBrush}" />
</hc:Watermark>
<hc:Watermark Mark="HandyControl" FontSize="30" Angle="45">
    <Border BorderThickness="1" CornerRadius="4" BorderBrush="{DynamicResource BorderBrush}" />
</hc:Watermark>
<hc:Watermark Mark="HandyControl" FontSize="30" Angle="45" MarkBrush="{DynamicResource DangerBrush}">
    <Border BorderThickness="1" CornerRadius="4" BorderBrush="{DynamicResource BorderBrush}" />
</hc:Watermark>
<hc:Watermark Mark="HandyControl" FontSize="30" Angle="45" MarkBrush="{DynamicResource DangerBrush}" MarkMargin="10">
    <Border BorderThickness="1" CornerRadius="4" BorderBrush="{DynamicResource BorderBrush}" />
</hc:Watermark>
</hc:UniformSpacingPanel>

<hc:Watermark Mark="Project" FontSize="80" FontWeight="Bold" MarkMargin="30,0"/>

<hc:Watermark Mark="{StaticResource GitHubStrGeometry}" MarkMargin="30,0" MarkWidth="200" MarkHeight="100"/>