Admiral Nelson never wore an eye patch over his lost eye.
The Spirit of Christmas played by Robbie Coltrane talks about 'penny farthing sheds." Prince Albert died in 1861. However, the first penny farthing bicycle was built in 1871. So, this incarnation of Blackadder is set prior to 1861. It may be that the spirit transcends space and time and has forgotten that penny farthings do not exist in this era. In any case, Ebenezer Blackadder wouldn't understand what he was talking about.
Queen Victoria is depicted wearing her stereotypical black clothing; however, Victoria did not actually begin to dress all in black until after her husband, Prince Albert, died in 1861.