The roof vents/tin copulas are great to have, although I wouldn't leave that as your only source of ventilation. Side vents or holes drilled under the protection of the roof lip, as high on the wall as possible (like where the roof peaks) work well together.
Exterior grade oops paint from Home Depot is usually inexpensive, with lots of room for experimentation (pour in some not quite gray, a little of this yucky purple..a splash of this white... ooh, pretty). Always stir the paint well and make sure the wood is thoroughly coated. Painting a lighter color inside helps protect the wood inside and bounce the sunlight around a bit.
Great job on the door! It looks super cool and well done. The locks are not predator proof by any stretch of the imagination- any raccoon or possum should be able to easily open that door. Spring loaded hook and eyes are good replacemants or additions (since those bolts also help pull the door to the frame in bad weather, wheras hook and eyes re more jigly). Can you add another doore opposite the nestboxes? In my experiance the more access you have the easier it is to clean (and more willing you will be to do it).
Windows are a great idea, especcially if they open. They let in light for seeing and laying, air for hot summer days. You can make one out of plexiglass and a wooden frame, and to make it open, add hinges.
Last thought. The coop is too small for four chickens. Two or three would be better. To grow your coop, you could take off the wall opposite the nest boxes and extend it out a few feet, taking off that side of the roof and leangthening it as well, making the coop 4x5 or 4x6. Do not do anything to decrease the space you have- feeers and waterers should remain outdoors or in the third nesting box. Make sure chickens can walk under the roost(s). Clean frequently. Chicken wire is not predator proof- any hungry animal can rip it with teeth and claws, so do not think you can make a 100% safe run with this stuff. It only contains chickens.