Hi sblackburn welcome to our forum!
For more information on how to use a skybox and what requirements are needed we have an article in our knowledge base as seen here:
Unfortunately we don't have a similar funcion, we do have a feature request for this where I will add your vote.
You can however use our Export Material-ID and Depth Channel function to create an Alpha channel to do this in post production as seen here:
In my opinion it's a basic feature in any rendering software, I don't understand how Enscape doesn't allow it yet... as an idea, you can look for some software that generates transparency in the enscape window, it's not the best, and the one that I have tried doesn't work with Enscape, but it's an alternative and I'll keep looking... I am wondering how to do an integration in a specific perspective from Revit with Enscape.
i hope enscape will soon come up with a solution to fit a model into a flat background photo
Add the image in post production. When rendering, create additional render paths (in capture settings) then add the image to the rendering.
If post is not a reasonable option, you can bring the photo in as geometry. The are even scripts that will create a "photo plane" that matches the camera viewing extents.
This avoids the need for post and also the unavoidable "fringe" that you will have to deal with.
For some eyelevel backgrounds this provides the added benefit of being able to animate the camera position slightly as still be believable.
