A while ago, Sega released a batch of PS4 themes for Valkyria Chronicles: Remastered, costing $1.99 each. The good news is that one of them has just been released for free on the Japanese PSN.
If you want to grab the free theme, you can find it here. Keep in mind that you need a Japanese PSN account to access the link and download it, but if your PS4 is set to primary, you can then use the theme with every account on the console.
The theme is static and doesn’t have custom music or sound effect, but it does come with custom icons. And it’s Valkyria Chronicles, which makes it automatically worth the download.