Even mouse pads come in a huge different variety of sizes, shapes, colors and of course qualities. You can purchase pads that are designed specifically to keep your wrists in a position which is comfortable for hours on end, or you can get pads that look like rugs and other types of carpet. I would highly recommend getting a pad for your mouse that is comfortable if you spend a lot of time at your desk. The number of injuries that occur in office workers during an average day is simply incredible. Of course, if you are taking regular breaks, your desk and chair (along with other office equipment) is ergonomically designed you are significantly reducing the risk of anything going wrong.
I would also recommend that you get a mouse pad that looks good. Today, you can jump online and get your own pads printed out. You can send a photo to a company online and they will print it on a blank pad for you mouse, and then post the pad to your door step. Some people like to put photos of happy moments, nice beaches or other settings, whilst others like to have something a bit different, like a pad for your mouse that looks like an oriental mat or something else a bit odd!
If you spend a lot of time at your desk you may as well make it a place that is enjoyable to sit at, and even more importantly ergonomic and comfortable to sit at. There is nothing worse than having pains in your joints from typing all day long, if it could be fixed by purchasing a 50 dollar keyboard, or a new mouse pad!