There is a stunning collection of 28 Megapixel 3D skyboxes at:
https://render.otoy.com/vr_gallery.php
You can load them as your VR Toolbox room backgrounds by:
[olist]
[*] Downloading them from the above web site (there is a download button on the right of each row).
[*] Selecting a Custom background in VR Toolbox and pointing the dialog to the OTOY file.
[/olist]
If the background has a nearby object, locking your translation might be of benefit (CTRL+SHIFT+L).