may just be me, but fairly often i look at my plating and think there is something missing…
for example, i got these dragon sushi rolls as an appetiser ahead of a late dinner, added a lil trout caviar and fleur de sel, but the plate looks still in need of something.
what would you add?
A parsley sprig. And that’ll be my answer to everything 
Dramatic sauce drizzle / lines on plate. That always makes things look extra fancy. I’m being semi-facetious, but that’s what I think of with sushi at least.
For real though - I’m the worst person to ask about plating suggestion as I want all my foods to fit on my dinner blate. But growing up eating family style food, plating was least of our concerns and I still cook and serve that way.
Bacon. Because bacon makes everything better. 
(I don’t do sushi, so would have no idea, but I think your plate looks beautiful!)
Nothing. I would just serve it on a smaller plate. I think it looks wonderful.
Smaller, different shaped plate would look fuller.
I’m in the smaller plate camp. Too much white space.
Smaller plate, drizzle of sauce, artfully arranged shiso leaf. Any one or combo of the above.
OK… Challenge Accepted!!
I’m totally trying that – I’ll cook the bacon (of course). How about a combination of bacon and avocado in a roll??
lots of very sensible suggestions!
Parsley.
Yeah, the Florentine salmon needs a parsley add - OR some bright green spring asparagus alongside (even though you have some spinach in the sauce).
Non technical/artistic suggestion:
Pine kernels. In a little dish on the side.
Another vote for a smaller plate. And maybe a scallion fan as a garnish.
pine nuts and raisins, and some plum coulis! 
Drizzle of sauce. A few long, bundled or chopped chives. Maybe an edible flower or two (nasturtium).
