Vid 1994

I'm wary about checking an index because that could be pretty brittle. vignette is a subdomain, so that one might be okay, but /images/thumb/ which is a subpath which means its index varies according to the name of the file and whether we're on prod or dev. How about I update this to a regular expression with some added specificity? I'll convert the legacy check as well to regex, but I don't think that one needs to be modified beyond that. No image should have /image/thumb/ in the name.