The Official MTG Snowstorm/Lore Thread

I'd say no. That's not really a case of heavily interacting with lore. That's a minor interaction that sent them on their way.
For instance just about any flake that's been fighting on Zendikar against the eldrazi might have reasonably fought alongside Nissa, Gideon, or any of the gatewatch at some point.
But saying that they're a member of the organization would probably be too much at this point.
That and every flake that's hung around the Izzet has been yelled at by Ral at least once.

I think of a few things:
>Mechanics that fit the character.
>Names and flavor that fit the character.

For example, let's say you're making a flake that cares a lot about speed and going fast. That's likely to be red, probably with an emphasis on aggro because y'know, going fast and with an emphasis on speed-based flavor.

Which leads to flake like this one being made. There's some minor screw-ups, like the Lightning Berserker and the waif could probably be swapped out for the messenger. But most of these fit well with the mechanical side of 'going fast' and the flavor side of 'going fast.'

And nothing of value was lost.

Be nice.

Oh I know the general feel, flavor and colors of the character, but how and where should I browse for and find actual cards that fit?

No.

Gatherer's the official card depository, although there are better places to do it that I personally don't use.

magiccards.info is great once you have it's search features down. And using it's images reduced to 60% for the preferred spells and 45% of the equipment section is always a good combo.

matchups when?

The guy is gone for a little bit.