[MarkFL]

You could create a plugin as follows:

Product: vBulletin

Hook Location: parse_templates

Title: Restrict size of images in signatures

Execution Order: 5

Plugin PHP Code:

PHP Code:

if (in_array(THIS_SCRIPT, array('showthread', 'private')))
{
    $template_hook['headinclude_css'] .= '<style>.signaturecontainer img {max-width: 500px;}</style>';
} 


Plugin is Active: Yes

Click "Save".