Marvelous released a brand new Senran Kagura: Estival Versus PS4 theme on the Japanese PSN. Not only it's sexy, but it's also free, so what's not to love?
You can find it on the Japanese PlayStation Store here. If you're logged into a non-Japanese PSN account, open the link in an incognito window. You'll still need a Japanese PSN account to download the theme (it's very easy to create via the web interface), and once it's downloaded, you'll be able to use it on any account.
You can check it out above and below. The theme is static, and doesn't have custom music or sounds effect.
[Thanks for the tip: Carlos Luis Ayala]