It never ceases to amaze me how much you dudes can think of...But all the same, I'm stoked!!!
Eowyn- would probably have....white hair (not old people white hair, cool white hair)
Arwen- Angular brown hair, and bubbly blue eyes
Frodo- Big shiny blue eyes, (ooh, shiny!!) :P and the same hair
Gandalf- Would be really tall, and would have kind of a childish smile, but would look really scary and formidable if he wanted to.
These are just my standards, please don't kill me.