Whichever change you decide to test, make sure you're clear on your goals. What are you trying to improve? Whether it's conversion rates, click-through rates, or something else, make sure you have a plan for measuring success.
Finally, don't forget that A/B testing is an ongoing process. The more you test, the more you'll learn about what works for your business. So keep at it, and don't be afraid to try new things. With A/B testing, you can never fail, only learn.