The themes for the parties that we offered were developed over the years. Repeat customers and the guests wanting their own unique party inspired new themes. We tried some that didn't work so well, considered some others ~ like boy parties, but I stuck with what was working and didn't push the envelope too far.
There is no limit to what can be added to this business, but my only suggestion would be to keep it high end and unique. I bought the cheap princess type dresses thinking I might venture into face painting and character parties, but most of those dresses still have tags on them. Just too common for what this business was all about. It could be an area for some exploration, but careful consideration would need to be given in order to maintain the high quality standards that you want to be known for.