What do I do to design my own iphone case?

I have a clear case I bought from amazon for my iPhone 4. I figured I could design my own case whenever I wasn't by putting different pictures in between it and the phone. The only problem is what dimensions and/or programs do I use? I have the windows 8 and it has the option of different sizes I can print if any of those works and paint if I need to change the sizing.

You can always customize whatever you want to customize.
You may like to visit my link here:

http://surfandbuy.weebly.com

OR
http://surfandbuy.weebly.com/viva-la-abstraction.html

and follow the link to see almost 36 designs

OR
http://surfandbuy.weebly.com/top-brands.html

Yes you can customize your iPhone by putting different images into the clear case. If you Google iPhone dimensions you will find what your looking for just edit them in Photoshop or paints and print them off…