If the site lags to load your div, it personally pisses me off to the point of raging nasal cliffhangers
Ellie Mors
ok but people have varying internet speeds, to the extent that someone's internet might be slow enough that the div loading might seem "normal" in comparison, or might be fast enough that the image loading really isn't an issue in the first place. People don't generally count the second(s) it takes to load a webpage on a site that is mostly text, and there's really no way for someone to gauge how much an image (or images I guess) contribute to that load time.
Before you placed the hard limit/cutoff on signature heights we had a guideline for image size for pretty much the same reason (aside from the eyesore of a 600+px signature height) and it would be super helpful to have something to go off of in order to make sure people don't get irritated at everyone having different ideas of what is too large in mind.
If it's not something you're willing to really figure out, in terms of what is actually the limit in terms of taxing the site loading, then just give us an arbitrary dimension (or just no background images in divs, idk, I can live with that). I don't think I've ever encountered a border image in a div that was larger, in terms of the image resolution from the source URL, than maybe 360x360 so I don't think that would actually tax the loading times on the site, but I also have zero knowledge of web design and have no way to know if they do or not.