Gavroche WordPress portfolio theme
Disclaimer: this theme is unmaintained. Feel free to use it, open issues and submit PRs though!
Mosaika.fr uses this theme as a parent-theme, with a couple of modifications done in a child theme.
This theme was created by myself for a collaboration with https://www.themesdefrance.fr, a French WordPress themes marketplace. TDF closed down before this theme went public, but I finally decided to make it available if anybody wants to use it... or even maintain it!
This theme was developed with flexibility in mind. It offers a settings page to customize it extensively. Its code offers many hooks to make developers happy!
But no documentation for now, so you'll have to dig into the code to understand what's going on. Feel free to open an issue if I can help you out.