I'm often torn on full-sized images in the postings (vs. choosing to display as thumbnail, which can then be clicked by the viewer, to view the full size).
I often access EBRF via my iphone, and many times while I'm out at a park during a long ride, where my cell signal is consistently weak.
A long thread like this, with dozens of full-size images in the thread, takes so much longer to open up than a thread of thumbnails. (I've never examined the hit to my cellular data plan, now that you mention it. But the only months I exceed my data plan's "included limit" are months I'm heavily on EBRF via phone.)
(But today, I'm using a PC, so it makes no difference to me right now