Create a circular selection using elliptical marquee tool. Create a new layer and fill it with blue to white gradient in linear mode.



From select menu select modify>>contract. Contract the selection by 10 pixel. Press Shift+Ctrl+D to feather the selection.



Press delete to remove the selection area.



Create a new layer above all the layers. Fill it with black color.From "Filter" menu select render>>lens flare. Apply settings as shown.





Change the layer mode to "Screen".





Select black as foreground and white as background color. Create a new layer. Select bubble brush from brush settings. Apply the brush randomly to complete the wallpaper.