and then just copy and paste the link in the comment box and itll pop up as a picture or as the link?
You have a couple of options. If you just copy and paste the link, the forums will (usually) automagically hyperlink it.http://forums.furtopia.org/Themes/head-left.jpg
You can also use BBC to explicitly create a link; this is a good practice, since you may occasionally find a link that the forum's parser doesn't successfully recognize. You can also make the hyperlinked text different from that of the actual URL. For instance, "[url=http://forums.furtopia.org/Themes/head-left.jpg]This is my link![/url]" produces "This is my link!
Last but not least, you can use BBC to actually display the image on the page. For example, "[img]http://forums.furtopia.org/Themes/head-left.jpg[/img]" produces this:
You can combine the [img] and [url] tags to create hyperlinked images; the [url] tag goes on the outside, and the [img] tag goes on the inside.
(*edit*) See also Mylo's post on the subject
, which goes into detail on how to use and get links from image hosting services.