I am very slow at building my trailer, but in so doing it this way I have had time to think out each part of my trailer. In some places I am stuck and in other I just need to find time. Between work and home improvements and family, I am slowly getting there.
My present project is the doors.
This brings me to Wiley windows that I will have, this leads to this addition to the Wiley Window. on the inside you are stuck with a wide cut out. My doors are hollow so I have an outside and an inside. Most of my light will come from my Trolley top so I can play with the design on the outer skin. This can be cut out as a image. one person did a Mickey Mouse head, most are square.
Halloween pumpkin designs (this being Halloween) and all the designs they can do with out it falling off are an example what what you can so on the outside.
Example of a normal one is michaelrsydney his unit is below

a really nicely done unit.
But there are designs you could cut out, now Micheal has an outside screen which I want to do too. But it does not need to be square although that would be the ezy way to do it. You could do a circular port look or a lots of holes to make a flower, Cut out the shape of a teardrop, a dog a cat or even butterfly, I drew some idea but have not loaded them onto my galley yet.
you can pull up on google images: "puppy silhouettes", "pumpkin carving ideas" pumpkin one hold more true because they are real cut outs.
In fact you could have the window as a full window and slide in cutouts of different images depending on what you want to say.