You can easily use Highslide HTML popups when you already have installed Highslide in your WordPress blog. See examples below.
How to use the Highslide Editor to create single type of Highslide gallery with NextGEN gallery. Gallery: Basic white
How to use the Highslide Editor to create multiple types of Highslide galleries with NextGEN gallery. Gallery id set_5 Gallery id set_4
Highslide JS
(the 4 images below is added with the NextGEN Widget)
(this video is manually added to a text widget)