- Gather some source material for your Normal Map, you can do this just by taking a photo of the ground or a wall with your phone.
- In Photoshop, make your texture seamless/tile-able by duplicating the texture. and gridding it to reveal the seams.
- Use the clone stamp tool to blend the edges.
- Use the offset filter and repeat the process to blend any seams in the texture.
- Once you have your seamless texture use Filter/3D/Normal Map to generate a Normal Map from your selected image.
- Save that image as a JPEG or PNG.