The problem with your image url relates to the variables, the data that comes after the ? mark. Urls that use variables are not necessarily a problem,
but in this case, the web site that hosts that image doesn't want you using it anywhere else.
The use of variables can sometimes simply provide information about how to display the image, but it can also be used for security purposes. For
example, if you find an image on some web site while being logged into an account, you won't be able to use its url elsewhere.
One way to get around this is to copy the image and then store it with an image hosting service, but they're not all equal. As you can see with
Eddie's post of an album cover using Photobucket above it's displaying it with a pain in the ass watermark. If you past that url in a blank
browser page it will display it without the watermark because that's for you. As soon as you try and post it within another web site, Photobucket
can work out that it's an indirect link and then mess with it.
There were a large number of images on the old Zappa forum that either never displayed correctly or displayed okay when they were first posted, but
eventually failed due to time stamp variables amongst many other reasons.
Plus, if you use a url for a resource from a web site, you have no guarantee that it won't get moved or deleted entirely at some future point.
The ideal forum would be one that allows image uploads, like on FaceBook, but that requires maintainence of large amounts of storage space and for
many forums this is financially restrictive.
The best way to handle images is to host them yourself, but that requires having your own website, which costs money. I have my own website for my
music project. When I want to post an image to a forum I link to a copy of it stored on my own web site.