Why thank you, your comments are flattering. I always try to take care not to let my OC's overshadow the canon cast.
The name... well, it's only a name, she doesn't really move at light speed, but I needed a cool nickname, something that had to do with speed... I would have used Accelerator, but that one is, well, unavailable for obvious reasons.
She was created merely because I have a mind that buzzes with these kinds of ideas. Most don't make it to paper, some do. I always have an OC in an anime that I make my own stories with, though most remain in my head. Keroko made it to paper because myself and a few other creators went brainstorming, I might write a fic with her some time.
If you'd like to read more, I have been creating characters for the Nanohaverse for some time now, and I had a short period of creating Strike Witches characters as well. The link for both archives is in my signature.
You mentioned your To Aru OC Keroko, and I thought she was pretty good: both in drawing, and in profile. Definitely avoided claims to overshadowing her more famous classmate, yet clearly a respectable fighter in her own right. Though maybe "Lightspeed" is a tad much...
I was wondering, was she made for a role-playing game, or just a fic? I'd be interested in looking at whichever, as well as any more character designs you've made.