Markush, great stuff, I too, love pushups. Parallettes and rings are my only tools of choice to augment bodyweight training. If you are interested, here is an old app I wrote for body weigth training, but you'll find HUNDREDS of exercises in it. http://learnthis.ca/bodymaster-app/exercises/shouldersback.html#page_pushup

The main app is here: http://learnthis.ca/bodymaster-app/

I hope you find it useful and some new exercises in there.