Try this:
To put in SharedPreferences
SharedPreferences sp = getSharedPreferences("myApp", Activity.MODE_PRIVATE);
SharedPreferences.Editor editor = sp.edit();
editor.putInt("NewBackground", idImage);
editor.commit();
To get the Preference:
SharedPreferences sp = getSharedPreferences("myApp", Activity.MODE_PRIVATE);
int myNewIntValue = sp.getInt("NewBackground", 0);
and finally use it. MyNewIntValue