Thanks the feedback. We're always looking for ways to make Bitbucket run a little bit faster. One of the things we've done is to defer loading of user and repository avatars until after the rest of the page loads, though they should still be cached appropriately. At the time we felt like the trade off of improving the load time in some cases was worth the small delay in being able to see avatars. But we're always reevaluating decisions like this, so I'll definitely bring your feedback to the team.
Oh, OK. If I have a choice between waiting half a second for the page to load then waiting another half a second for the images to load, versus waiting a whole second for everything to load all at once, I guess I'd want to go with the former option as well! ;)