Custom eyes can be a lot of fun to make - it's fairly easy to get a decent result, though getting a truly amazing, realistic eye takes a lot of trial and error.
What you will need
- Iris Texture Map Tutorial - Another more advanced Photoshop tutorial showing a different technique to generate realistic eye textures.
General Tips and Tricks
- If you are creating eyes, consider using Knightskykyte's sclera PSD - she has created a layer-separated image that you can use to create a very realistic shading to your eye - just pop in your iris and highlight and you're done!