Does anyone know how I would be able to add items onto a task in a sublist like you would on a transaction? I would like to be able to assign multiple items to our marketing photographer via a task that will populate his calendar.

This would have to be a custom record with at least two fields. Alternatively you might be able to link to an order of a photographer is responsible for the entire shoot

Yeah I was thinking of doing something like a custom Opportunity form that multiple items could be added to. I had been trying to make a custom record with an item sublist but was not having much luck. By at least two fields, do you mean multiple list/record fields, one for each item?