특정 버튼 안에 이미지 넣기
Button button = new Button(mContext);
button.setText("Close");
Drawable close = Drawable.createFromPath("/data/icon/image.png");
close.setBounds(0, 0, close.getIntrinsicWidth(), close.getIntrinsicHeight());
button.setCompoundDrawables(close, null, null, null);

custom button
imageButton.setBackgroundDrawable(getResources().getDrawable(R.drawable.icon_chkon));

button toggle image
http://developer.android.com/reference/android/widget/ImageButton.html