By trade, one of my duties is Housing Code Inspector. Not that I'm selling doom and gloom but, I have seen this before.
Make sure you check with your landlord before you do any changes. Get the OK on paper. What you consider an improvement, May come out of your security deposit when you leave. You should take plenty of photos now and make sure their dated.
Once you get all the OK's don't get too fancy fixing up someone elses property. (Paint goes a long way)