I would say they are quite quick usually but the R&R contest just ended and they were super quick with approvals for awhile leading up to the deadline. So they might get slower until the next contest since that is when they get approved super quickly. When did you submit them? Has it actually been that long? Also for some people you can’t preview it in your phone/tablet because of background and overlays not being approved. Mine has never done that but just try doing it in the portal and it should let you. 
You can always go back to the scene later. They should be approved soon if you uploaded them a few days ago.