Considering the comment under my previous post, I had a better incentive to look at more formats. So here are two of them.
Since both are Amiga formats, here’s a summary picture:
First, Zoetrope Animation. The same ADF image containing BACKFLIP.rif has also the player sources (C + M68K assembly with comments). I have not studied them too closely but the main peculiarity of the format is that like its namesake it operates on image columns, employing simple RLE (and skip for inter frames). Also while it calls its format RIFF it has rather different structure (and may even pre-date more common RIFF by several years). And it seems to support different bitplane modes, as well as HAM.
Then, IFF VAXL. This is a conventional IFF with video properties inside VXHD chunk, PAD0 for padding, TMCD being always the same (is that a time between frames?), COLS containing something looking like some 12-bit palette entries, BMAP being of a constant size, SAMP probably containing PCM audio. But what about image data? Since it has a constant size fit for a 6-bit uncompressed image (and has 6 in the properties), I suspect it’s just Rohschinken uncompressed HAM (and trying to decode it as such results in a recognizable picture).
That was surprisingly easy but there are many more formats to look at.