Pinkie is a tough one to imagine only because most bubbly party things are usually girlhood in nature. I'll try to think of some ideas tobtry to help. I have seen some boy versions around and saved on my laptop, unfortunately my graphics card went out so I don't have access to that right now.
I myself am working on concept sketches for my boy-Rarity. Hopefully that can be done by Sept for BFF in Austin.
WIP to be debuted
San Japan: Laxus Dreyar (Fairy Tail)
Alamo City Comic Con: Hawkeye (Fraction run),
Street Vigilante Red Hood