Kneeboard - mark position on custom page?

I know how to add custom pages to my kneeboard, and I'm thinking up ways to use it more because it's very handy.

One thing I wasn't able to find information on - if I add a custom map image as a kneeboard page, is it possible to tell the game that it's a map, so I can mark my position on it?

Or can you only mark position on the default map pages?

Thanks!