Most of them can probably be avoided for the purposes of an AVIF file, but patent US20160232939A1 [2] in my reading seems to be about in-container signalling to express relationships between a "static media item" and "one or more entities" that together "form a group", and "indicating, in the file, a grouping type for the group". The patent appears to be written in a way to allow this definition to encompass, say, a thumbnail and a bunch of frames thereafter, or, say a master image and a set of pictures derived from it, or alternate camera angles of the same thing. Some of these techniques sound like stuff we've seen before, but as is common in patents, the precise wording of claims is often key, and this is where patent lawyers come in.
A thorough look of the AVIF specification [3] and the patents registered with the MPEG LA about this format [1] is likely wise before any widespread deployment that makes use of advanced features of the HEIF container; using it to hold exactly 1 'one-layer' still-image is probably fine.
Additionally, in my reading [5], the HEIF reference software released by Nokia [4] includes a patent grant for non-commercial evaluation, testing and academic research only.
[1] https://news.ycombinator.com/item?id=19874321 [2] https://patents.google.com/patent/US20160232939A1/ [3] https://aomediacodec.github.io/av1-avif/ [4] https://github.com/nokiatech/heif/blob/master/LICENSE.TXT [5] https://news.ycombinator.com/item?id=19874368