Almost all games have powers that have an extended activation time. In almost all the cases I've seen the character just sort of stands there as the power bar/counter/power up sound all play and then the power fires. I'de love to see a more "Lina Inverse" effect for this time rather than characters always just standing there. For example, the character floats up into the air and spins in place.. or SOMETHING other than just standing there.
How about the most obvious:
1) Moving your arms around like casting a spell?
2) Shaking as your attack point grows brighter and brighter.
3) Doing a Kata.
4) Switching weapons or ammo, maybe even putting a rocket on the end of your gun.
5) a quick weird costume or color change
6) Changing Shape like Liu Kang before his Dragon Fatality.
I'm sure that some bigger and/or flashier animations for the "bigger" spells will be available at some point, maybe not at launch since it depends on what aesthetic themes they decide to do.