Its not the background that really matters, its the pictures are out of focus, see if your camera has a macro button on it, its usually a flower icon.
Looks like it might be a crack. Are you sure it is? I expect it to go all the way to the rim but am having trouble making out whether that is happening.
This 1837 has a crack in a different area. There are actually several cracks in different locations. I don't believe they add to the value in dollars and cents, but they do add a coolness factor.