Google Chrome Extension: Theme: background image not fills the entire browser screen

[Josue B]

 I'm creating a theme for Google Chrome.

 Current result [ image below ].

 I want...

01- the image fills the entire browser screen.

 
image [current] details: (background.png).

width: 1024px;

height: 750px;

 I tried using the following image size...

width: 1920px;

height: 1080px;

  but the result has not changed.

 what's wrong with my manifest ?

 Can anyone tell me where I went wrong?

 
OBS:

01- I asked on stackoverflow, but no one answered.
02- I read the documentation

thanks.  (google translate)

Manifest.json

{

	"version": "2015.0.1",
	"description": "Nanatsu no Taizai Theme",
	"name": "Nanatsu no Taizai",

	"theme": {
		"images":{
			"theme_frame_overlay": "img/overlay-40.png",
			"theme_toolbar": "img/toolbar-120.png",
			"theme_ntp_background": "img/background.png",
			"theme_button_background": "img/button_30.png",
			"theme_tab_background": "img/tab.png"
		},
		"color":{
			"frame": [10 , 17 , 27],
			"toolbar": [10 , 17 , 27],
			"ntp_text": [255,255,255],
			"ntp_link": [255,255,255],
			"ntp_setion": [10 , 17 , 27],
			"button_background": [10 , 17 , 27]
		},
		"tints":{
			"buttons": [0.33, 0.5, 0.47]
		},
		"properties":{
			"ntp_background_alignment": "bottom",
			"ntp_background_repeat": "no-repeat"
		}
	},

	"author": "Josue",
	"manifest_version": 2
}