Generally, there is little way for you to get around this issue. You do not necessarily need to create a new "Table" in your database for tinymce, but you will either need a new controller with the create action or you could probably latch on the action on an existing controller, but that is a bit messy.
Here's a github repository that has the source code for the demo (the author of the gem wrote the demo, so it's good), it has pretty much everything you need : https://github.com/PerfectlyNormal/tinymce-rails-imageupload-demo. It uses Paperclip to do the actual upload of the images (which does require the table).