The photo is the sole content of the website, which is hosted by tumblr.
Wal-Mart is specifically upset over the website's domain name - www.walmart.horse - according to the site's creator, Jeph Jacques.
On his personal website, Jacques claims the company sent him a cease-and-desist letter accusing him of trademark infringement for using Wal-Mart's name in the URL.
"You have registered, without Walmart's permission or authorization, the domain name(s) 'walmart.horse,'" the letter states, according to Jacques. "The Domain Name incorporates the well known Walmart mark in its entirety, and, by its very composition, suggests Walmart's sponsorship or endorsement of your website and correspondingly, your activities."
The letter orders Jacques to immediately stop using the domain name.
In a response to the letter, Jacques argued that the website is an "obvious parody" and falls under fair use.
"Publicly available images of a horse, a Walmart store, and comical music make it clear that the site is meant to be a joke," Jacques wrote to Wal-Mart. "I would be happy to provide a disclaimer on the website explicitly stating this. If you have any requests for other animals you would like to see added to the image on the website, I would happily comply!"
We reached out to Wal-Mart for comment and will update when we hear back.
It's not unusual for companies to go after people or businesses that appear to infringe on trademark rights.
Starbucks, for example, made headlines two years ago after sending a cease-and-desist letter to a tiny brewpub in Missouri that started selling a beer called "Frappicino."
Starbucks has also sued a coffee vendor in Bangkok for using a logo that looked similar to its own.