If you want to go with an art thread, you can just edit your first post with new art whenever you update and then make a post on the thread that lets people know. Or, you can just post the art as a reply whenever you update (this might be easiest).
Art threads are a great way to keep your work together. But sometimes, people miss updates because they don't remember to check back. Creating a new thread whenever you have new art is always an option too, it often gets the best exposure that way.
Either method has pros and cons, so it's just personal preference.