There are no limits on the size of the image, colour technique or depth. However, you should take into account that the photos will be judged on a large screen, but that does not mean the files need to be huge.
Do not forget to include your name/nick and post at the party. The videos will be screened on Saturday night. The Organisers reserve the right not to screen those productions whose contents are offensive (specifically, ours) or are deemed to be inappropriate.