Signature Problems

[Hrothgar]

I've been wanting to add an image to my signature, but it hasn't been working. I looked at the list of signature permissions below, and it says I'm not allowed to upload images for signature. Is there any reason for this?

[Jale]

Basically, you can't upload an image as a signature, but you can post an image using the [IMG] tag.

[Lefteris_D]

Is there any reason for this?
There are several free image hosting services that you can use for such a task including images to your posts.

[Hrothgar]

The thing is, I did try the image tab, and I was using the image from a hosting website. It works inside the post. I kept the picture 500X100, and kept it below 50 kilobytes.

http://img209.imageshack.us/img209/907/brrawlbannerqx8.jpg