Metabox with multiple fields added by user and upload box

Here is how I’ve done it. No changes to the save function are needed. I’ve been trying to save data from both fields at once, thats why it didn’t worked.

<input class="upload_file" type="text" size="45" id="picture_%1$s" name="picture_%1$s" value="%6$s" />
<input class="upload_button button" type="button" value="Upload File" />
<input class="upload_file_id" type="hidden" id="picture_%1$s_id" name="items[%1$s][picture]" value="%7$s" />

The value stored in .upload_file_id is attachment ID (%7$s == item['picture']).
The value displayed in .upload_file (%6$s) is wp_get_attachment_image_src like so:

$img = wp_get_attachment_image_src($item['picture']);
$img = $img[0];

And then we set %6$s to be $img. So in database just the attachment ID is stored, and we display link using WordPress function.