s it possible also to create a sign-in/log-in area for my followers so they can upload their info

There is no upgrade you can purchase from WordPress.com that will change your blog into becoming a wiki or a forum by use of plugins. Wikis are based on the idea that the crowd, collectively, has a greater sum of knowledge than just one individual. No one person owns or rules a wiki. The wiki model is one where all members are able to add and edit material to build a knowledge base is quite different than what Discussion boards and Blogs are structured to do. See: WordPress.com Forum Options

can my followers uplaod pics of their own?

Your readers can submit comments containing links to images and embeds you as Admin of your blog can approve them or not.

You can add users to your blog. See here for user roles and see here for adding users.