I may have a solution. Once you have created a basic image you are happy with, make sure you keep the name box empty in 'prepare' before you create a back up from it then put the first ipad on to prepare alone with the firs number in the sequence. Once this is ready and you are happy with it, put a number of ipads on to prepare. If you follow the sequence here very precisely
http://support.apple.com/kb/HT5185?viewlocale=en_US&locale=en_US
then you should be ok.
If you have already started preparing some ipads ignore the fact that it is numbering them all the same as it prepares (it picks this up from the basic image). If the prepare stage is successful it will give them the sequential number they had originally. However you must keep them all in sequence
Some pointers:
- If using sticky number labels on the back of the ipads label them after set up is complete
- Don't set apasscode before preparing ipads
- If you get a message that it can't prepare one of the ipads, look at the ipad concerned and switch it on; it may be that you have already set a passcode - if so log in and click 'trust' in the dialogue window, then go to the Mac computer with configurator on and click to close the error window; the ipad should then appear in configurator
- Most importantly keep checking any ipads that are preparing; some installs will take a long time especially if you have an update to the iOS
- If you get and unable to prepare message look at it! One I kept getting was "Unable to send ProceedWithKeybagMigration command to device". I'm not sure but this may be because the device has a different iOS version than the ipad concerned. Put that ipad aside and prepare it later when the others are complete
- Don't click the stop button if you have several ipads preparing - it stops everything not just the one you think you have chosen!
Hope these help you - produced in the process of preparing several iPads for a primary school and I now have 20 completed