Gallery hints can be found here:
Forums at Splitcoaststampers
As far as the thumbnail - go ahead and click EDIT, and then re-upload. It will go back through for approval, but then the whole image will be there again. If you have two of the same-named files, we'll catch it the next time we scan for duplicates. Then you won't have the thumbnail missing.
If the pic is the same as another, but with a slightly different file name (like name1 instead of name) . . .that's cause you clicked the upload/submit button again while it was submitting.
It's happening to most everyone, so you are *so* not alone in your frustrations!
Hopefully Daven will have a nice announcement soon. ;)