I created web tool to generate seamless patterns - https://www.arbuuz.com/draw/index.html
To cgenerate seamles pattern you need PNG file or files.
The first image is generated with this web tool and the second image is created from the first image. Elements in image is created with Blender and rendered images are saved as transparent PNG files. Background added in Photoshop.
The second image created from generated seamless pattern.