Gateway Backup with Custom CSS

When taking a gateway backup, does the custom CSS files in the directory {InstallDirectory}\data\modules\com.inductiveautomation.perspective\themes
go with the gateway backup?

It does, yes

What about items in the web server folder like images.

I don't know with certainty, but would presume so. Docs page for reference.

You could always spin up a local gateway on another computer and test it to be sure.

Edit, deferring to Phil's response below. Didn't realize the web server stuff was not in the data folder.

Pretty sure not. That isn't within the data folder hierarchy, and serving images from the web server folder is explicitly unsupported functionality.