You can disable or uninstall the Media Viewer app and install/enable the Gallery app if you prefer it.
It is worth mentioning that you cannot have both enabled at the same time.
I’m afraid there is none.
Anyway, I’ll continue using the gallery app, at least as long it is possible. For me, it’s the preferred solution, even if ownCloud decided to go on with media viewer. And there is IMHO no need for further development in gallery app, it has all the features I need and no issues that I’m aware of.