Figure 8s are usually fun or you can set up a "trail class" like course with different obstacles (poles, mazes, weaving standards, "broken bridge" which is when you make a zig zag of poles on the ground and see how narrow you can make it and still turn your horse through it)
Mix it up and do different patterns etc or try and change where you ride
I love serphantines and cone work. There are barrel racers at my barn so sometimes I like to do the barrels, posting trot to the first, sitting trot around the barrel, Canter to the next, post the trot around the barrel....etc. keep it spontantious and you’ll have more fun!