This is something done on a state-by-state basis. While FIRST may be able to petition for license plates in New Hampshire, I don't think they could do it for the 49 others.
We tried in 2008; in the end we narrowly missed out because FIRST is headquartered in NH and we couldn't tie it directly back to Indiana. Since IndianaFIRST is now a registered 503(c), we'll give it another shot.
It's a labor intensive process, as outlined in the linked thread. But if it works, it's definitely worth it - as advertisements and as a fundraiser. Good luck!