How to make a duck pen more exciting for my birds?

[LostGosling]

I'm going to start breeding Blue Swedish Ducks for pleasure and show, but don't know how I'm going to set up the run. I need to figure out how to make my run less "prison like" to my ducks. My home made chicken pens are all dirt and are, as my mom calls them, "drab". I've done everything I can to make them less boring, but no matter what I do, they're still just dirt pens. I wound up turning most of my chickens out on the yard today because of the guilt. My run is going to be full of sand and river rocks for hygene (If I leave the pen full of clay and grass, the first time it rains a bunch it'll be a mud pit.), and larger stones and branches for decoration. They will also have a pool to swim in. Will this pen be "drab" as well? Any inexpensive tricks on making the pen more habitat like for them?