I tried a few really obvious backgrounds (Even a mario background for fun) and found a soft subtle background gave the best effect, although it looks like I went too far. It looked fine on the few screens I demo'd it on, but I'll update with a higher contrast background soon.

Try using something more colorful like a landscape or bokeh so that the perception of parallax feels natural and impactful. I had totally missed the parallax had it not been for the comments here.

I noticed it much more when I turned my laptop screen brightness up all the way. Maybe something to consider testing if you pick a new one.