Let’s learn how to create an illiustration. You can get your favorite photo and try to do the same steps.
Let?s create a new document with dimensions 500x400 and 72 dpi. Using the instrument

Continue using the same instrument 

All of them having the same colour:

Continue create triangles:
We?ll get the next picture.

On a new background create a nice star using this instrument 

The colour code is indicated again with red.

Make several stars of different dimensions, but of the same color.

And several stars of different colors:

We?ll combine our stars with the triangles and we?ll have the next picture:

We’ll add some luminescent stars using the instrument Blending Options where we?ll choose Outer Glow and set out like in this picture: