Don't mention the Shadow of the arm. 

In November 2012 the Liverpool museums page said (but doesn't say ist anymore): "[...] On the table there is spilled salt, symbolic of the blood which will later be spilled. The shadow of the arm of the foremost brother is cast across this salt, thus linking him directly with the future bloodshed. [...]". The URL was http://www.liverpoolmuseums.org.uk/online/pre-raphaelites/lorenzo/symbolism.aspx

In June 2013 I noticed that the new page the shadow is gone: "[...] salt, symbol of life, is spilt on the table; [...]"