I was surprised by the current image here: https://www.renderosity.com/news/?viewStory=18824

You can use a speedster character of your own creation or one that's in the public domain, but you can't use one that's covered by copyright and trademark. At the very least, you should blur the chest symbol and change the colors to blue or green or something that doesn't look like the Flash or the Reverse-Flash.

Hello,

This image was actually pulled from our fanart gallery so it is okay to use in a promotional sale image.

When it is not okay to use a fan art image is when you are trying to make money off of the image itself and in this case, we are not...we are using it to promote a sale we have going on in the Marketplace that has nothing to do with the actual image itself.

Thank you for your concerns and have a wonderful day,

The problem is you're using the image to promote a sale. That's commercial use. I realize you're doing this innocently, and odds are good DC's lawyers won't notice and will only give you a warning if they do, but it's problematic—it certainly does not fall under fair use, because the use is purely promotional. I'm not a lawyer, but I've been a professional writer for over 30 years, so I've had to learn more about trademark and copyright than most people.

"When it is not okay to use a fan art image is when you are trying to make money off of the image itself" — but that's precisely what you're doing. It's an ad for a sale, designed to generate income. You're not promoting the piece standalone; you're using it to talk about your sale. Willshetterly is right on this one: you really shouldnt be using this.