Wonderful!! I love bargellos!
More contrast is optional...if you want a wider swath of a certain value (like a wide pale swath with a narrower dark gradient) then there's nothing wrong with similar values...
if that's what you're aiming for.
But if that's NOT what you're aiming for - I think you're right, these pale ones in your sample are a little too close.
It looks great though, I hope you post pics of your next one.
I've made 2 so far and can't wait to find time to make more.