Yes, asset mods have been available for a little while now. It's a feature called LayeredFS in Atmosphere. Someone ported the patches needed to firmwares 4.x.x and 5.x.x but the patched kernel files cannot be distributed legally. If you're on 5.x.x check this thread out: https://gbatemp.net/threads/how-to-use-layeredfs-for-backup-loading-what-games-work-dont.507510/I want that portrait mod for Stardew Valley, is that possible yet?