1. Physological needs: warmth, water, food, rest, toilets, hygiene, accessability, shelter
2. Safety needs: security, safety (both in the practical and the psychological sense)
3. Belongingness & Love needs: while this is something we cannot control, making space and time for actual contact between people might be a good idea. Can be combined with the things in point 1
4. Esteem needs: Feeling of accomplishment (the actual content of the event needs to give the audience something new and valuable)
5. Self-actualization: Again something we cannot easily control, but there might be ways of having the attendees actually do something themselves in a creative and/or productive sense. But my guess would be that if you rocked the first 4 points, this one is a nice extra.
Too many events focus mostly on point 4 and forget the importance of the first 3.