Backdrop or No Backdrop for outdoor ceremony?

It is hard to tell from that picture what the background in your photos will be. If you like the scenery behind you during the ceremony, I do not see why a backdrop would be needed. If you think the background is boring, maybe an archway with flowers would be a good option?

For my ceremony, we will have a gazebo behind us. It is small so we will not be inside the gazebo, just in front of it. I don't love this (we were originally getting married in a church so it did not matter) but I plan to add flowers to the gazebo so I like it more.

Maybe an arch or a coordinating piece of fabric hung from the tent? I feel like it needs a focal point to draw attention front and center.

If anything, I would add an arch of some sort. The simpler, the better in my opinion!

I think I would put garland or leaf and floral swags along the rail or hang a decorated hoop. An arch seems like it would add more lines to the bottom. You could also use some large potted plants or taller grouping on the floor to follow the line the shrubs behind the chairs seems to create to keep eyes going in that direction