could you post a pic

My understanding: You didn't find any problem functionally, but you feel this looks old & need some brightness & change in this. My advise: 1). Remove towel rod, shift it next to tub or behind closet & have full length mirror, which will make your space double & reflect natural light as well thus makes the space more bright. 2). Get couple of plants (small plants or bush type or creepers which doesn't occupy much space on floor but grows vertically). 3). Get some artifacts made from bright colored glass, can flower vase or wall hangings or glass tiles etc, these can be of yellow or Bright Orange color these are to be hung on walls opp to mirror or pasted(3M tape both side glued) if you are using tiles. 4). Get a mat of same color as artifacts & place between tub & closet. these all are easily done by yourself. OR if you can afford to then replace only green tiles & floor tiles if you wish to OR all tiles.

How big is the window? Why does it need protecting, exactly? What's in the bathroom now?

I think you will be fine with that choice in a small bathroom and I'm sure it's actually relatively common. Here is one example I found on houzz and it's a combination with have in our small carriage house bath as well. For floor we did white hexagons with a repeating black pattern. http://houzz.com/photos/740269