One of the many things that VAs can do to increase their value to clients and potential clients is to learn new skills and specializations. When you have a larger skill set it makes you more valuable, more marketable, and widens your potential client base. However, one common pitfall you may want to avoid is to market yourself as a generalist or "Jack (or Jill) of all trades".
Trying to be everything to every client out there does not work. As the saying goes, a Jack of all trades and master of none, is not what you want to be known for. What would be best for you is to select your ideal target market, specialize in that VA niche and allow for other skills that will complement what you plan to do with your business.
When you brand yourself as an expert you inspire trust in those you work with. For example, you can work in the real estate industry and you may only choose to do transaction coordination or listing coordination. Those are your specialties. And of course, you may choose to work on everything from listing to closing for your clients but still have a specialty in those areas.
Specializing makes you much more valuable to your clients and creates a reputation that is strong in the industry.