>>5776
I've experimentally disabled the subject requirement to see how many people start accidentally making new threads again.
The new thread form's button says "New Thread", and the reply form's button says "New Reply", but that's not enough to stop people from confusing them. It might be possible to make them more distinct with CSS, using a hacky selector. I'll look into adding text or something.
>either a subject line OR an image
That's not currently possible, and probably too niche/weird to get implemented.