1. You can start off by choosing the size of your background. Mine is 150x150 pixels.
2. With your background, go to filter> render > clouds.
3. Then go to filter> pixelate> Mezzotint. Select "long lines" on the drop down menu. Here's what i got.
4. After that, go to filter> blur> radical blur>. Change the amount to 100. Choose "zoom" and "best". You should get something like this.
5. There you have it! All you have to do now is change the colours to what you want it to be. Go to image> adjust> hue/saturation (Ctrl U). Just adjust your colours there and there u have it!
Sry if i wasn't clear enough or something. Its my first time making a tutorial.