I've been using an "at-a-glance" page for my long-term planning for years - a single page, simple organizer that sorts my objectives and lesson ideas by media, style, subject, connections and more. This format really helps me plan because it is so easy to see if there are big gaps in my media usage, or one area where I may be overloaded, for example.
Here's the order I use:
1. Write in my most important objectives that are specific to the unit/grading period.
2. Hit Pinterest for all the ideas I saved, and see where they fit in. Also look at the previous year's list to see what I want to repeat.
3. Check off all the matching media/styles/subjects/connections, and look for gaps or excesses. Figure out how to balance it out by changing media, etc.
5. Once you have your year planned and balanced, this makes it easy to begin the more in-depth (yawn) lesson plan writing. wah-waaaah. Oh well, at least the first part was fun!
I just added this "Year-at-a glance Art Lesson Planning List" to my Teachers Pay Teachers store - try it out if you need some organization with your long-term planning! http://www.teacherspayteachers.com/Product/Art-Lesson-Planning-List-1482079