Insert the grass and several trees along the lower edge. I used two kinds of ready brushes for this.

Fairy Night photo editing in adobe photoshop cs

Represent the design now, which will be situated inside the eye. I combined a ready design and a butterfly's picture. To separate the butterflies from the background they are situated, just mark them out with Polygonal Lasso Tool and cut them out with Edit – Cut (ctrl+x). Insert them on a new layer: Edit – Paste (ctrl+v).

Fairy Night photo editing in adobe photoshop cs

The butterflies need to be discolored: Image – Abjustments – Desaturate
 
(shift+ctrl+u). Increase their brightness and contrast, using Edit – Abjustments – Brightness/Contrast.

Fairy Night photo editing in adobe photoshop cs

Make up now a design with a ready brush and butterflies. Copy the layer and apply Filter – Blur – Gaussian Blur. Merge the blurred layer with that one where it is situated the design itself, applying Layer – Merge Down (ctrl+e). Change the layer's type on Multiply.

Fairy Night photo editing in adobe photoshop cs

Take a sky's photo now.

Fairy Night photo editing in adobe photoshop cs