That's an unusual question. The only thing I could find online on this matter is the story of the first ico created back in 2013 by J.R. Willett. This guy is the only one creator of ico and I couldn't find anything about any team that was working with him on Mastercoin project, but I still find it rather suspicious. Of course, there're often leaders and people might not know anyone apart from this person related to the project, but I doesn't mean that there were no other developers helping him with all that stuff. Nowadays any ICO needs not only a strong team with multiple people, but also a number of advisers on the project, so I think going solo is not the best idea.