osmarks.net research teams designed code to download and embed all images ever posted (and not deleted) from Reddit (excluding NSFW, ads, etc), using streaming processing to avoid having to persist intractable amounts of data to disk. Unfortunately, it is still necessary to store embeddings, and the high cost of flash and electricity means a full run (it was tested at 0.5% sampling) has been postponed until local winter.
It's already far too late.