We got a good deal on plain windows that are simply glass in a frame. They do have a decorative wood grid on them, although I forgot what it's called. I think they look nice.
We framed a hole to size and attached them with hinges and latches, on the outside. Three have the hinges at the...
Mine has five!
Ours are hinged and swing open completely. It keeps it cooler in the summer, as well as providing light. They love looking out of the windows when they're inside, too.