*peers closely at the bottom, looking for the in-scale crabs and other marine life*
Kidding! I think you did the right thing with the prop wash, that display you have is VERY eye-catching as is. Ed's right, try some wake detailing. I use acrylic paints for that because they dry quicker, but maybe on the smooth plastic of your base oils would be better. Dunno.
My only thought is, is there going to be a top over this to keep the dust off this awesome creation?