You can launch Crop intent by start activity for result and retrieve it in result and then use wallpaper manager class. like this
Uri imgUri=Uri.parse("android.resource://your.package.name/"+R.drawable.image);
Intent intent = new Intent("com.android.camera.action.CROP");
intent.setDataAndType(imgUri, "image/*");
intent.putExtra("crop", "true");
intent.putExtra("aspectX", 1);
intent.putExtra("aspectY", 1);
intent.putExtra("outputX", 80);
intent.putExtra("outputY", 80);
intent.putExtra("return-data", true);
startActivityForResult(intent, REQUEST_CODE_CROP_PHOTO);
and use Wallpaper manager in your onResult function
Also keep in mind that It depends on the device whether that device is support it or not. This Intent action is not part of the internal API. Some manufacturers provide their own Gallery apps and so there is no way of knowing whether or not the user's device will recognize the Intent.