You can do several things.
If this is a project that you are building over time then you could start a developer's journal through which you can keep people updated about your progress and seek some feedback on your game as well post links.
You could ask for specific answers to specific problems in the right forum for example a question about artwork would be asked in the Visual arts forums.
Posting in the Your Announcements forum though is probably not the best place for your needs.
If you are seeking general feedback on the game itself...what tends to happen is you create a thread in the Game Design forum with the appropriate link providing some information about the game and requesting feedback.
Hope this helps
So I think Your Announcement forum is the best place to show projects (even unfinished).
My biggest concern was not where to post, but if I could post this kind of project.
Developers Journal is a better place to show projects than here in YA? Thought it was just for articles or technical documents.