when trying to link to an external image for my sig, I get an error saying I have linked 2 images, and can oly link one. Not sure what is generating this, as I am only trying to link to one external image...I am using the same tags to link images as normal. [img]external link, then closed tag. Am I doing anything wrong?

In your user CP go to "Edit Options" and scroll all the way to the bottom. Make sure the "Message Editor Interface" is set to "Enhanced - Full WYSIWYG Editing". See if that helps.
If not, make sure you are using the direct link to the picture. I'm assuming you've uploaded it with a photo hosting site like photobucket? If so..they provide a link with the IMG tags already on it. You should be able to just copy and past that into your sig.

What is the image you are trying to link to? Looking through your DeviantArt pictures, I believe it is this one:
http://fc08.deviantart.com/fs51/f/2009/299/9/b/blaz_by_DarrenMcD.jpg

If that is the case, you have to keep clicking on the image to get to its actual location. In this case, you were attempting to link to:
http://darrenmcd.deviantart.com/art/sig-141512263
while the actual link url is:
http://fc08.deviantart.com/fs51/f/2009/299/9/b/blaz_by_DarrenMcD.jpg

There is a limit of 1 image in signatures, but I do not think this limit was the cause for your concern. I have updated your signature to show this image.

thanks boss