It sure is nice to hear that people still consider the feelings of us dial-up users. I've had image-viewing disabled for so long that I'd forgotten it was an option.
In the best of all possible worlds, I'd love it if the discussion forums contained only thumbnails that linked directly to the full-sized images (if that's what the poster wanted). I don't know if the board software could do that, but it would be a lot more informative than "you_name_it.jpg... 275k". As a dial-up user, I find that 20k-25k images load pretty fast, and a 300 pixel limit in size is big enough to see what an image is about. The example below is colour, 20k, 300x300px., 20% compression.
It'd be simpler to just limit size, and i think the standard used at photo.net (511px, 100k max IIRC) is a reasonable compromise. A photo laden thread on photo.net is also pretty slow on dial-up, but here we have the option of limiting the number of posts displayed per page, so we don't have to wait for all 70 images to load.
Anyway, thanks for thinking about it, here's my sample thumbnail..