Wow, those are some HUGE rainbows!
Honestly I think the tank looks great, and you've obviously found a happy medium as all the plants seem to be thriving. My only suggestions would be to make the rocks and driftwood more prominent, try and arrange them in some way so they are a focal point of the tank rather than being stuck in the back. 55s are tough to aquascape since they are so narrow front to back. I've worked for a long time to try and get mine to at least appear as though there is a foreground, mid ground and background, it seems like with these tanks you can have 2 of the 3. Maybe try reducing the number of plant species and try some larger bunches of your favorites. This will let the plants spread out some and I've found that the most impressive tanks have larger clumps of fewer species.
If you really want some inspiration, check out some of Takashi Amano's books (any of the Nature Aquarium World series)....they'll have you drooling but have some great ideas.