The around the clock baby shower theme focuses on baby's activities during a specific time of day, such as breakfast time, play time, bath time, dinner time, bed time, etc.
When you send out the invitations, assign a different time such as 8 am, noon, 8 pm, to each guest and write the time on the invitation. Explain that they are to purchase a gift that will be used at that time of day. For example, 8 am could be a daytime outfit, noon could be a baby dish, 8 pm might be bath items. You get the idea. Make sure that in the invitation you tell the guest to write the time of day on the card or outside of the gift.
For a somewhat similar baby shower theme, you could substitute a room in the house for an hour on the clock. The guests would give things that would go in that room, like a blanket for the nursery, bath items for the bathroom, or toys for the family room.
Another takeoff on that baby shower theme could be to do seasons, or months of the year, or days of the week. Care will be needed in picking out gift for other seasons or months; you will need to take into consideration the baby’s growth, both mental and physical.