I was wondering if is there a way to enable to the user to send content using a form, to select different options like categories, attach images and so on, and after submit the content save as a draft in to the post.
I use CRED from Toolset to create forms for users, which allows to create posts (any type) and upload image. See http://wp-types.com/ This is paid plugin.
Some Form plugins allows you to do that (like the mentioned by @mitogh).
You can check this article: https://premium.wpmudev.org/blog/wordpress-post-frontend-plugins/