How to make pictures worth the wait?
Two things, it seems, are desirable. From the engineer's perspective we must strive to make images lighter:
On the other hand, though, we must strive to make images heavier, make them communicate more. Images need to do a better job of adding to our information, of illustrating when they do -- or they need to charm better, to provide another dimension of communication, to be both eye- and mind-candy.
While we wait for more conclusive studies of how images work on the web, it makes sense to play both sides of the issue: try to minimize download time, while offering viewers rich, memorable images.