Create a dreamy background with your Photoshop skill is not so hard! In this tutorial, you will learn how to do it with just a few simple steps. 

Step 1: Prepare a 800x800 pixels document with black background. Use the gradient Tool(G) with  "Diamond Gradient" mode  

Step 2: Now draw a big "star" like this (just hold down your mouse and make a long move!):

Step 3: Select Filter > Distort > Twirl and "twirl" about 256⁰ CW

Step 4: Select Filter > Distort > Polar Coordinates and select "Polar to Rectangular" option

Step 5: Select Image > Rotate Canvas > 180^o

Step 6: Now press Ctrl-U to open the "Hue/Saturation" dialog box, make sure to tick on "Colorize" checkbox and use these settings:

Here is the result!