Sure, some sites have you pay for a high-quality scan you can actually print of a game whose original case you probably wrecked or lost, but there's one specific site where you can grab box and cover art, retail or custom (and guides too), without spending a dime. If you haven't stumbled on it yet while browsing around, I'm talking about TheCoverProject.

The project is a big community effort that's been going since 2021, and files get uploaded straight to the site (so downloading them to your device is literally just a click away). Naturally, there's a forum where you can ask for covers you're missing, or maybe share some of your own. From old and rare systems like Amiga CD32, Atari Jaguar, MS-DOS, NeoGeo, PC-FX and Turbografx-16, all the way to the newest ones like PS5, Xbox Series X and Switch 2, this site has it all —at a handy 300dpi (good for printing)—, so make sure to check it out regularly (link below).

Hope this comes in handy.