Link behind a thumbnail to an external URL - how to realize?

Hi guys,

is it possible to place link behind a thumbnail to an external URL?

That means, I have a sub-album that has the same content as a gallery installation at an other server somewhere else.
I now would like to save the time for administration the same content twice.

In a sub-album of my main gallery I would like to place a thumbnail with a link that opens a new browser window with the address of my second gallery installation at an other server.

Any help is very appreciated!

Thanks and regards,
Tom