There is a limit to how large an attachment can be, this is so the site doesn't become slow by having to store everything.
The other method is what I prefer, uploading images to photobucket, image shack, Flickr, etc, this does take quite a long time at first as you have to get used to it, but once you've used it its great. By storing the images online they'll always be there, that means you don't have to keep them on you phone etc, it also allows you to edit images, like blurring number plates. Just copy the image code onto the thread you're writing

There a how to thread on uploading images in the 'how do I do this' catagory
