Usually, whenever I used the [ img ]link here[/ img ] code, I could use any image URL from anywhere and it'd post. Now it's seems that only images from certain places are working and others just break. I'm not alone in this happening. Would you please look into this?

Some sites don't allow you to link to their images. Could that be the issue?
Dexter by ❤
it's not that the images are from sites that don't allow you to link to their images, because i've seen this happen with images from plenty of websites that worked fine before, like tinypic:

i believe the issue has to do with whether or not sites use https; subeta doesn't seem to want to link images without it. however i think photobucket, even though it uses http, still works.

is exactly right.
this is because web standards dictate that an https web page cannot embed materials that are served over http. most browsers won't even allow it. so since subeta is now served over https, http images will not work. if you look at the page source code, you'll notice that even though you used an http link for that photobucket image, we've embedded it in the page with the https link. which is why it works. tinypic apparently doesn't serve images over https, and there's really nothing we can do about that. :/