Firstly let me say that I like the way this plugin is going. The short time since it has been available it has already seen various features added and issues fixed. Thanks.
Having said that I am really keen to see the following features added:
1) An option to conditionally enable this plugin on selected pages when using "all" or "external".
2) An option to exclude certain URL's from showing thumbnail tool-tip.
Hope you are able to find the time to include some or all of the features suggested above.