What kind of filename do they have? How big are they?
My guess would be that they’re Android thumbnail files or some sort of hidden metadata file. Possibly some raw jpeg because all the parameters are expected to be fixed size so they didn’t bother with the header. Or it’s a custom header.
But even then, that’s a lot of zeros for an image format.
Does it seem to have a JPEG header later in the file? It could be a header followed by a normal JPEG file too.