Number 4: Why is her shirt pulled up? She's spanking her butt, not her chest. Unless the shirt was restricting her motion in some way.....
Number 3: Why aren't her pants down? Or off? If she's going to go to all that effort to self-spank, why waste it on smacking denim? She's denying herself a good, stinging impact that way.
Number 2: Why a belt? I should think something like a paddle or a hairbrush would be easier for her to aim and control.
And the Number 1 thing I wonder about as I look at this picture is--
Why didn't she just ask ME to spank her?