How to make a green retro style background image in Adobe Photoshop in just a few steps.

1.
Start with a new blank document, then go to filters -> rendere -> clouds

Now go to image -> adjustments -> levels and drag the right and left handles closer to the middle as shown below.

2.
Now go to filter -> pixalate -> mosaic and set it as shown below.

3.
Now we have a pretty fun effect, and we will make it better now.

Go to filter -> filters gallery and locate the filter called accented edges and set it as below.

4.
Again go to the filters gallery and now locate the filter called ink outlines and set it as below

5.
Again go to the filters gallery and now locate the filter called water paper and set it as shown below.

6.
Now we will change the colors and saturation of the image so go to image -> adjustments -> color balance and the hue and saturation panels, and drag the handles as you please to change the colors and saturation.