Chris Hanson:
A lot of people think QuickTime is a “video format,” but that’s not really accurate. Video and audio playback are applications atop the QuickTime container format; the container format itself is a means of representing multiple typed tracks of time-based media, each of which may have their own representation in the form of samples interpreted according to their own CODECs.
All of these are represented within a file as atoms which represent well-identified bags of data with arbitrary size and content, making it very easy to write general-purpose tooling and also to extend over time. (The last major extension to the low-level design was in the 1990s, to support 64-bit atom sizes, so it’s quite a stable format already.)
QuickTime, like TrueType before it has proven to be quite a well-designed format. If you’re looking for inspiration for a binary data format these feel like great candidates.