hmm. That's interesting.
When watching the memory of the game play and especially our larger game. I notice that per layout the memory usage is different. In our highest animated room the memory usage is 250mb and in our first room which has the least our memory usage is closer to 100mb. So memory usage is different. If all the sprites were loaded then our game would likely use about 1000mb at all times. So that's not the case.
Maybe what is happening is that C2 downloads ALL the assets, but stores them in the offline cache. This would account for for the AJAX to download all the images.
Also aren't the sprites on export on sprite sheets anyways. So it seems all the sprites have to be downloaded anyways. C2 on spritesheet can't really be selective to what parts of a sprite sheet are transfered. So it seems all the assets are going to get downloaded due to lack of selection. So if you can examine the AJAX call on the sprite image then it sounds like your monitoring a preview.
While I like the idea of only downloading the assets between layouts when needed and having a loader screen. It just doesn't soudn like it's feasible with the graphics being packed onto a sprite sheet. it sounds like al the sprite sheets need to be downloaded at the beggining. Which does add a lot of download overhead. :|