I know most people don't use alt in their images in vBulletin, but actually this mod should work even if they do. I just checked your site (the one in your profile) and found this example link in one of your posts (by viewing the HTML source)
HTML Code:
<img src="http://www.pb5th.com/pbkidz10/log/051611.jpg" alt="!!!">
The problem is that isn't a valid xhtml img element though it works on browsers just fine... the proper tag should look like:
HTML Code:
<img src="http://www.pb5th.com/pbkidz10/log/051611.jpg" alt="!!!" />
I assume you're using some type of Mod or BB Code to produce those images. If you edit it to put the proper xhtml closing (the "space, followed by the slash, followed by the closing square-bracket) or " />" this mod will recognize it as an xhtml <img> tag and ignore all keywords inside of it be it filename or alt code.