Steam has decided to change its rules and image guidelines due to developers using review scores and award logos in their lead images. This clouds exactly what the game is about, or even what the title of the game is, causing confusion among buyers.

New Rules Steam Devs Must Follow
It has become more and more popular for developers of games to show off their ratings, "10 out of 10! Would buy again!!" in their images to grab the attention of gamers who may be interested in purchasing their game. While it's great to see the game has a lot of clout and a good rating, it makes finding the concept and title of the game inherently difficult.
To avoid naming and shaming anyone, Valve decided to make use of the images they commissioned for the Steam Summer Sale 2022 minigame by using them for mock-ups. Taking those commissioned images, they then put examples of what they considered bad practices on four of them and used a fifth to show an example of a game following the new set of rules. Here is an example of that:
Valve is constantly changing and revising its rules for content, much like they did with crypto games, but more recently, they took notice of issues with images developers were using to advertise. As of September 1, 2022, the guidelines for images will change, and developers must adhere to these new rules. Steam mentions that they already have spaces available to show off the game's ratings and quality, and the images should no longer be used to tell players about that information. The company states,
" Recently, we've noticed more text, award logos, and even review scores being included by game developers in their graphical asset images. This made us realize our guidelines haven't been as clear as they should be. As a result of not having clearly-defined rules, we've seen additions to graphical assets that are creating a confusing and sometimes even inaccurate experience for customers."
As a part of Steam's new guidelines, developers are not allowed to mention their awards within their images, as well as add in any discounts or promotions available in text form to their photos. Devs are not allowed to advertise other products within their images anymore either, which includes sequels or other games in the franchise. On top of that, they go on to say that they would rather text be kept to a minimum completely, as it covers the most important part of the image; the game itself. Here is an example of PlayWay showing a discount within their header image:

Their list of General Graphical Asset rules is much shorter, as it just states that the devs must include both the games logo and title within the photos, and meet the dimension requirements. All of the graphical asset photos must also only include PG-13 appropriate artwork, not rated R images. This isn't the first time they have cracked down on adult content being too off the wall, as they previously changed the rules for the games with sexual content involved. Though, it is worth noting that Steam has been pretty inconsistent and lenient with their rules on games that showcase explicit content, enforcement on rules can likely be expected only in egregious cases.
On top of all of these changes, Steam does mention that those who want to mention updates or seasonal events may do so in accordance to their Artwork Overrides rules. These images also have rules to follow, which include a clear start and end date to an event, which cannot be greater than one month, and the image must be uploaded as an Artwork Override for it to be valid. This is only used to describe new content to the players, and all text must be localized into the same set of languages that the game supports at the very least. For DLC content or in-game events, the only text that will be allowed on the image must be in direct correlation to the DLC or event, nothing more. These images also only take over the slot for a set period of time.
Some publishers add text to their images more than others, such as Square Enix, who regularly show us images like this:

Finally, Steam states,
"Any game not adhering to these rules may have limits to visibility within the Steam store and will be ineligible for featuring in official Steam sales and events."
For a full list of all the rules and updates, you can visit steams official website.