[BirdOPrey5]

You could make a custom BBCode... say call it imga (for image-alt)

Then you could type in [imga="The alternate description here"][nparse]http://somesite.com/image.jpg[/noparse][/imga]

In your BBCode Manager-> Add A new BB Code
the replacement would be:

<img src="{param}" alt="{option}" border="0" />

Use Option: Yes
All Disable Options: Yes


Edit- Actually I think you can call it IMG jsut like the built in tag and if you use the option it will use the custom tag, if you leave out the option it will revert to the default tag.

Edit 2 - Confirmed it works even if you keep the same name, IMG, for the tag.