I Googled "arena patterns and exercises" and found a link to an old Horse & Rider magazine article that I liked & saved for reference, called
Additional reminders to keep indoor rides interesting came up, as I sifted through online info:
• Desensitizing stuff (ex. hula hoop/dragging things/carrying things)
• Practicing Reining/Equitation/Dressage tests (some can be found online)
• Riding stirrup-less
• Lengthening strides
• Riding bareback
• Lengthening strides
• Riding bareback
I also liked some of the arena patterns the Icelandic riders do: http://iceryder.net/arena.html
An additional search of "equine cone patterns" led me to some Gymkhana images. I liked these a lot! I found ton's of idea's, and general riding skills to work on. Scroll down to see the pattern images:
This is where I stopped looking. With this plethora of new idea's & reminders, we'll never be bored riding indoors again!!