The property ItemHeight of the "System.Windows.Forms.TreeView" .NET control allows you to set the height of each item in your TreeView. It's a bit surprising, but .NET libraries developers have set a maximum value for this property.
If you set an item's height to greater than 24 pixels, the value is automatically reduced to 24 pixels before being processed. To bypass this limitation, you can override the TreeView class and the WndProc method, and then modify the parameters of the TVM_SETITEMHEIGHT message.
The source code that can be downloaded will help you to better understand the concept.