They are tracking you with IP address tracing while you upload the images and for imgbb also this is
privacy statement for them so using them over TOR is fine with the postingimages.org as it's working fine at this time.
On the internet don't trust anyone. I mean all the site set cookies to collect customer information and they make money out of it, they improve user experience from it. When you are in clear net checking up your email, you are giving them away your information. Even when you are browsing a site without entering anything, by just loading it you are giving them information. It's hard to avoid. That's where TOR helps. But since not everyone wants to be TOR friendly it's hard to use it for most of the service we use. So you make a choice. It's a choice like being with android or iOS. Some apps are not available in both platform so you sacrifice when it's not available for you or you have both.
I use clear net for many service but when it's cryptocurrency, I always like to break connections the possible way I can.