Looking for a ‘loading’ spinner solution

I’ve got a couple of pages in which I’m pulling in some external content into an iframe. The content loads fairly slowly and I’d like to show a loading ‘spinner’ symbol or similar in or over the iframe space while this takes place.

Any ideas how I can do this? (I know there are plenty of images for this out there, but I’m looking for info on how to actually incorporate this ‘item loading’ function into a WordPress page).

Cheers,

Jon