Nice first mechanical! The KUL is such a great stock keyboard.
What modifications are you looking to do?
Well, after only having this board a couple months, the keys are already getting that greasy/shiney look to them so I think I want to upgrade to some better keycaps. I also like the look of using difference color keycaps; in particular, i smash the F5 and F9 keys a lot to execute code, so having them a bright color like red, with a nuclear or skull symbol would be cool.
Might also consider painting the case. I'm not really sure what other popular mods there are aside from adding LEDs or swapping switches/keycaps.