Valve have been peculiarly silent lately considering everything that's been going on around them, but at least the company wasn't completely idle. The company confirmed that the long-awaited Steam Library overhaul is a few weeks away.
"The new Library brings together a player's experience with a game and new content/communications from the developer and community in a richer, more visual layout", they wrote.
Steam's stylish new Library is a few weeks away from beta testing, so Valve called for developers to start uploading new assets to suit the new capsule and header formats.
Note that Valve will still create a "fallback treatment for both the capsule and header treatment", which means if you're a lazy dev - GabeN will automatically do it for you, but the differences in image formats are best handled by the source.
Considering that these changes will be Steam-wide, older games particularly run the risk of not fitting with the new Library, so developers are encouraged to redo their entire portfolios on Steam.
Steam Library's capsules will require 300x450px size, or 600x900px, where the latter is reserved for 4K monitors. Valve said that the latter is not mandatory at the moment, but will be in the future.
The Library's hero banners require 1920x620px, or in the case of 4K displays 3840x1240px.
In the new system, logos are uploaded separately, which allows for a slight parallax effect, i.e. when background images move slightly slower than foreground ones, creating an illusion of depth.
Developers will choose where to position their Steam page logo, and while Valve advise bottom left, you'll be free to experiment with the placement.
Additionally, your Steam page's logo placement is likely to look a bit different once the window is scaled, so Valve advised playing around with that too before deciding on the final logo position.