Fun things to do when riding?

My horse is green he is doing w/t very well though and my trainer has been cantering him with no problems for the past 2 rides and thinks she found the trick to get him to not gallop off so next week we have arranged for me to canter him in a private lesson. But I want some fun things to do w/t with him because we're both getting bored with it! Right now halted I lay on him my feet on his hind end, walk with my legs infront of the saddle flaps (I plan to trot him like this tomorrow), walk side saddle (my balance does not allow for trotting), w/t , walking with just a halter working on his whoa and turning off my legs, 2-point, posting, sitting, no stirrup work through all 3 of those, all of these we do while bending through cones and serpentines, we have done leg yeilds and turns of the forehand/haunches, jumps small jumps (not and not with no stirrups im not used to his jump enough for that yet). All of this has helped him relax and just focus on what im telling him to do and not freak out when im doing some odd thing on his back, but now he's used to all this and I want some other things to do! any ideas? we also do ground work but im just looking for riding ideas