I'd say for the next contest like this maybe only one person gets sent the images and that same person posts them to the contest forum without any names attached. That way to the rest of the people it's as anonymous as possible. Ideally a way to bar people from then commenting 'that ones mine!' would be helpful too.
We sometimes do contests like this, particularly if the membership is voting on them. However with a judged contest it's not as big a deal and having it open gets people more involved in the process.
Ideally as well judges wouldn't have access to the topic area until the submission end date passes. So they all see everything with a new set of eyes at the same time.
Two of the three judges only checked the thread once I contacted them for their picks. The third was very active here. I don't think that any of them were swayed by when any given sonic was posted. Not a bad point though, something to think about.