1. Your game has a pretty cool and unique art style – with the gritty, grayscale, retro vibe. I would showcase that and make that the main aesthetic of the page, e.g. as the background. Also I wouldn't reuse the game logo as the background and keep it at the banner only.
2. The top banner seems pretty huge and takes up most of the vertical space, I would make a slightly smaller version with reduced height so that the game viewport still sits somewhere in the middle of the screen. Keep the owl logo though it looks awesome.
3. Change the page font to something more fitting with the aesthetic
4. Lastly, follow the tips above regarding screenshots and GIFs. It's an action game so you should be able to get a few action-packed GIFs and screenshots. At the minimum one for each game scene (e.g. 1 for main game loop, 1 for select upgrade scene, etc).