If you're working on images, doing lots of mouse-button clicking, I will say it's safe to assume you may have some wrist pain. Or maybe arm or hand pain. Maybe it keeps you up at night. I have the solution: A tablet.
I started using one when I used to work for Schawk (formerly Ambrosi), here in Chicagoland way back when Star Wars Episode II was still in the theaters. It took awhile getting used to it. Eventually I bought my own (for my old Blue & White Macintosh G3). This was an old ADB port used model from ebay. What a deal!
Almost 10 years later, I've purchased 3 more (one broke while transporting to and from a client's worksite).
I suggest going no smaller than the 6x8 inch or 6x9 inch size model (unless you don't do alot of Adobe Photoshop or Illustrator work). Anyway, whichever model you get, I know you'll be happy.