I recently married a couple who planned a romantic wedding that included the bride's wheelchair. The chair itself was fully decorated, and the bride was fully decked out in "fairy princess" bridal attire. I suggested that the groom and I also be seated, and eventually it was decided that the entire wedding party followed suit. The wedding party simply walked in, and gracefully took their seats, with the groomsmen each seating the respective bridesmaid until everyone was seated.
It occurred to me that this arrangement would work for any couple that doesn't want to risk standing for too long a time, or perhaps includes a partner prone to fainting.
The effect was wonderful, no less formal or appealing than any other arrangement, and the photographs are gorgeous.