Look up lightshows by Teardrop and wonton in youtube...you'll have plenty of inspiration.
Regarding digits specifically, look up Kai digits on youtube...loads of stuff to work on. I think he's got a page you can subscribe to or maybe its their website, floasisdotnet on youtube. The most difficult part of digits is the dexterity. You need to be able to control your fingers individually to get the best effect. Cool thing is you can practice anywhere, anytime. I practice at stoplights all the time...

I still suck, but am hella better than I used to be.