You can set any image as a custom background for the editor and all tool windows in IntelliJ IDEA.
Configure a custom background image
Press Control+Alt+S to open the IDE settings and then select.
Click the Background Image button.
In the Background Image dialog, specify the image you want to use as the background and click OK to apply the changes.
For more information about the options, refer to Background image settings.
Background image settings
The Background Image dialog has the following options:
Either specify a local path to an image in your file system or a URL to an image on a remote server.
Specify the relative opacity of the image, where 100 is completely opaque and 0 is completely transparent.
Use the icons to select where to place the image:
This project only
Select if you want to use this custom image as a background only in the current project.
Editor and tools
Configure an image to be used as the background of the editor and tool windows.
Configure an image to be used as the background when no files are open in the editor.
Clear and Close
Clear the background image and use the default background.