One way I use occasionally is upload a photo to an upload site such as
http://www.imageshack.us and then link it to my post. On one of the pages at image shack there are link boxes with different types of links for different applications, message boards, thumbnails, etc. One of the link boxes contains a direct link to the image. I copy and paste that into my post like this:
[img]link_goes_here[/img]
Then you can put as big of photos as you want on here....
You don't need to use imageshack. There are others such as Photobucket, Webshots, etc. The reason I don't like those is because I don't want or need an online photo album...