Falconloft says:
Image limits: This is a holdover from earlier days, aimed at preventing spammy image posts that didn't really do anything else. The three image limit might not be practical now, as even one image of sufficient size can impact performance. We'll be looking more at this as well.
Then why not be more focused on the size of the image rather than the quantity of images?
(Cue old man speech)
I started working in web development back in the 90s. Back then, everyone was on dial-up modems. Even if you were at work, there was no guarantee that you'd have "high speed internet," which was a T1 line (good for 1.5 Mbit/s). A rule of thumb back then was to keep pages at
60k or less. Nowadays, that's good for avatars or thumbnails.
Where am I going with this? That experience taught me to optimize images for the Web. I host all of my images, so I'm conscious of how much space they take up. You won't see me inflicting multi-MB size images onto GP, despite the fact that internet speeds are so much faster now, but I can see where others would. Cheap memory and today's high speed internet lets people be lazy about file sizes. My son doesn't so much as blink at downloading anything that's less than a GB (to phone or PC).
Other than avatars, what other image hosting does GP do? I can't see how GP can reasonably enforce a size limit on anything that's hosted elsewhere. At least with the avatars, there's code one can put in to constrain file size.
If you're worried about site performance based on offsite-hosted image size, educate the users of the site on image optimization.
(End old man speech)