Loading message for pop up! plugin

The title pretty much says it all, but in case it doesn't, I'll explain: I noticed that the pop up plugin loads the content pretty slowly. It may have to do with the larger file size of what it's loading, but either way, it would be nice to have a simple phrase in the background of the pop up that says "loading" and perhaps with a little moving graphic of some sort so you know the site/pop up hasn't frozen.

Thanks!