I'm not suggesting tighter restrictions on images in general. However, there's one user who has a signature image that feature large, rapidly-flashing colors (which give me a headache, and I don't even have epilepsy.), and another user with a large, relatively lengthy converted video file that causes slowdown in my browser.

Again, I don't want to impose tighter image restrictions, but these two extremes are a problem.

Just report those users and a mod will kindly ask them to remove it.

I was trying to compose a post and wanted to use the feature, but I'm not sure if it even works anymore.

As Geno said you can PM one of us and we'll handle it on a case by case basis