The fun thing about resolutions is that it doesn't have to be about just yourself. In fact, quite a few people I know take the new year to better their properties. Even if sprucing a place up is impractical due to the winter months, making your plans to do so is always a good idea. Styles and trends change so much that it can be hard to keep up. If you keep pushing it off, it can easily become a job that seems daunting and almost impossible. However, if you revisit your décor even just once a year it can seem like a nice, quick and easy task.
If you believe that your building has no issues in regards to how it looks cosmetically, perhaps taking a quick look at all of the internal workings around this time of the year would be useful. Make sure that your electrical work is up to code, be sure that the visible plumbing is nice and tight, and double check that all of the flooring is safe, be it carpet or hard wood. Look at the caulking in the windows and around the sink and tub. If it could use a cleaning or be redone, take some time to do that. These are simple things that will need to be done from time to time.
If it has been a few years since your space has had its last coat of paint, think about refreshing it. This is especially true if the building is friendly to smokers or if pets are allowed. A fresh coat of paint can help to make any apartment look well kept.
Think of what your rental property would have on their New Year's resolution list if it were a person. If possible, pull a few of these from time to time and help it along. After all, buildings can't do it on their own.