Hard to tell if Java Moss on the wood or a Riccia foreground would be too much. The moss would be the easiest to work with, but I don't know if covering your hardscape would be an appeal or distaste. I, personally, like the look of your wood.
You can use the plastic knitting grid stuff to make Riccia easy, however. Just sandwich the Riccia in between two pieces, sewn or stapled together, and let it grow. You can then move/remove it to suit your needs.
I tend to like letting things grow in a bit before adding new plants. It lets me really see where I need to put my focus. I like to design my 'scape to where I get an even amount of attraction, meaning "where does my eyes focus first". Currently, in your tank, my eyes move to your plumbing first. This may decrease a lot after a little bit of grow-out time.
Bottom line, I would let it grow out a bit. Aside from the plumbing (which you already know about), it looks pretty good to me!