What's your "ImagesByName" folder path ?
What did you enter in the MetaBrowser Options for Images by Name ?
Are you using the most current version of MetaBrowser ? If not, use the 4.01.09 version. Delete the MetaBrowser cache in Options and Refresh the Cache.
What does your "ImagesByName Location" line MediaBrowserXML.config file look like?
If you download the Actor images from the links I gave you, you should see that when you extract the downloads - there are subfolders...