Personally, the photos are not that good, in my humble opinion, but we can hope that someone might recognize one of the two suspects.
One suspects has a white cap on, this is suspect number two who is seen leaving the backpack on the ground, probably bomb number two. The other a dark cap this is suspect number one who is suspected of placing the first and smaller of the bombs. (Fox News)
The FBI failed to give the logos on the caps, perhaps they don't know or could not identify the logos. You cannot tell much about skin color or nationality from the images, other than the two are not Black.
Daniel Greenfield writes:
These are the latest photos and video released by the FBI of the two men they are looking for. As before, assume that nothing is final until it is. You may have trouble with this link because the FBI site appears to be down.