These are just some short notes on some of the needed info to create a Cover for the no-choice Facebook Timeline, which apparently takes effect on 10 March 2012 - ready or not!
Facebook says that the cover must be at least 399px wide. That is all they said.
However googling around, it seems that the ones that seem to be most stated as the right size is:
Addendum: 4 Mar 2012
Hah! I finally found Facebook's official statement of the Cover dimension:
Article written on 3 March 2012