The moment you hit the Attachments link there's a plain listing of the file types allowed AND Restrictions:
Restrictions: 25 per post, maximum total size 2000KB, maximum individual size 1000KB
It's up to the user to do the simple maths to ensure the 2 Mb and 1Mb maximums aren't exceeded.
Unlike other online sites this forum doesn't upload your selected files until you hit Post, instead it spits it all back at you if you've exceeded the restrictions.
BTW Shock, why would you want to upload such large images, do you really need such detail or something ?