I like the idea and orientation of your tacky boot rack...so why not get something with a back that serves as a sort of room divider? You could put a cushion on top and have a seat for taking off shoes...Obviously you'll want the back to be finished. Also, light fixtures are very easy to replace. Get one you love and put it up. Keep the existing to put back when you move out. Both of these things won't break the bank and you simply take them with you when you move... I assume you'll be patching the walls? Ask the landlord for the paint so that you can match it. You can hang a picture...just don't have a thick frame...it will be fine as your door can only go as far as the doorknob allows. If you don't want to have a picture, these are fun and work well... I like the tree as you could add Command hooks (from 3M) to the branches here and there for your keys and scarves and hats....

Good idea to add doors to converted garage and use it as an office/play room. If you use the sectional in the original living rm., can you remove the middle seat area to make it shorter? Then put it in front of the living rm window and your t.v. and console opposite on wall next to pantry bump out. There will be more walking room to office/playrm. Unfortunate your sectional ends can't be reversed for this reason. Or keep current sectional in office and put new furniture in original living area that will fit the space, such as a shorter sofa under the window and two chairs. Or shorter sofa to make an entrance corridor along front door area and chairs in front of window. Add taller bookcase to bump out area and another chair angled along back of kitchen wall next to t.v. console.

About 4-5" below the mirror. The center of the mirror should be 55-60" off the floor. I think thicker is better to balance the size of the mirror. I'm not sure you need to make it longer.

Have you thought about wall paper on that wall you definately need a better light and IMO no Edison bulbs any hwere if you really care about colors you choose.You have some nice choices but then you cast a yellow light over it all. Change your bulbs to LEDs in 4000K before doing anything moore you will be surprised how much better everything looks at night.