Nice tank and setup!!! I like that ludwigia, but you are right, I think it would look better in a larger tank. I feel some rotala magenta, or something colourful, but more delicate would take it's place nicely. Also, you could try a smaller sword, like melon instead of amazon. There are some very gorgeous red varieties as well that stay almost dwarfed under high light, at least, for me. I am a huge fan of swords though.
I love your staurogyne as well. Are you going for a carpet on the left side? I love how you can just chop off the tops of this plant and just replant them. They just keep growing new heads and spreading along the substrate. Great low maintenance carpeting plant imo.