Let the plants fill in a bit before you decide to add more. Those swords will pretty much fill the background.
I would normally recommend a black background. It makes everything you want to be looking at pop out, hides any equipment and gives fish a better sense of security. But, your tank looks good without a background. Something to consider though.
In case you arent aware, aquarium plants are cultivated immersed in water, rather than submerged. As such they had ready access to CO2
and need to transition to being underwater and having the CO2
largely cut off. The leaf structure has to change. What tends to happen is, leafs start to die off, this is called melt. Its possible you might lose all your existing leafs to melt. New growth should be tolerant of the new environment. You need to give plants a couple of months to transition to know if they will be good or not.