OK I've added the old Curve Theme in Mobile format, then added a Mobile Mod which will redirect you too the Curve Mobile Theme when you access the forum using a Mobile Browser.
So now you will have the benefit of the new Theme on a Desktop/Laptop and the benefit of the old Curve theme on your Mobile or Tablet, that is unless you use Tapatalk.
Those who want to use the new theme on Tablet or Mobile, just have to scroll down to the bottom of the Curve Theme on your mobile and tap 'Switch to Full Site'.
Remember to clear your browser history, otherwise it will direct you too the new mobile theme until you do so as it has cached it.
Unfortunately the only other Mobile Theme available is even more simple than the Curve one and has a charge attached to it.
IF YOU PREFER THE OLD FORUM THEME, then you can choose to use the old click 'Profile' > Forum Profile > Modify Profile > Look and Layout
Then change 'Current Theme' to 'SMF Default Theme - Curve' which was the original theme.