I've submitted 2 screenshots of my battle stats, and they've both been rejected for the same 'reason'. It wouldn't surprise me if gamehag rejected it because I got 7 wins instead of five... So how do you people do it?!
Do not use snipping tools. Set your game to windowed mode, complete the task and take a screenshot by using Alt + PrintScreen, paste the photo and saving it in a photo editor, and submit.