cresteds would be ok, You can do Rankin's Dragons, croc skinks would be cool with a nice water area, you can make it look like a stream bank and what not.
im really considering a land turtle. i want to stay away from fully aquatic. i really likem ornate box turtles and such. i will also be able to move the turt into my 75 gallon(4'x18" floor space) because the rhino is going to be going into a 4x3x3 grow out enclusure that im going to be building out of an old shipping crate(stay tuned for that)