Jocelyn has some very good points. You could also increase the number of repetitions, do the movements slower, combine 2 or more exercises to increase the intensity and the variety (for example do pull-ups/pushups/bear crawls/dips all in the same set or mix jump squats/lunges for lower body) and in some cases put on a backpack to make it more interesting. Also changing the surface where you are doing you exercises can have an impact (for example hard floor or cement vs. sand). Most of the exercises can be done by going uphill or downhill as well.
There are countless ways in which you can perform body weight exercises in order to make them more difficult and more fun.