Post the in progress photos in your own personal gallery. The campaign folder is for the 1-3 pictures of your completed entry. If everyone posted their in progress shots (say 5 throughout the build) into the campaign gallery, then it would quickly grow out of hand.
When uploading completed photos, you should name them consecutively so they stay together, i.e. Vadster1, Vadster2, Vadster3 or Sabota, Sabotb, Sabotc...
Avoid naming your photos by model type, i.e. M4a, M4b, M4c since more than one person may build the same vehicle.